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Department of Veterinary Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri 65211
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ABSTRACT |
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 Top
 Abstract
 Introduction
Methods
Results
Discussion
References
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The purpose of this study was to test the hypothesis that increased flow through coronary arterioles increases endothelial cell nitric oxide synthase (ecNOS) and Cu/Zn superoxide dismutase (SOD) mRNA expression. Single porcine coronary arterioles (ID 100-160 µm; pressurized) were cannulated, perfused, and exposed to intraluminal flow sufficient to produce maximal flow-induced dilation of coronary arterioles (high flow; 7.52 ± 0.22 µl/min), low flow (0.84 ± 0.05 µl/min), or no flow for 2 or 4 h. Mean shear stress was calculated to be 5.7 ± 1.0 dyn/cm2 for high-flow arterioles and 1.6 ± 1.0 dyn/cm2 for low-flow arterioles. At the end of the treatment period, mRNA was isolated from each vessel, and ecNOS and SOD mRNA expression was assessed using a semiquantitative RT-PCR. All data were standardized by coamplifying ecNOS or SOD with glyceraldehyde-3-phosphate dehydrogenase. The results indicate that ecNOS mRNA expression is increased in arterioles exposed to 2 or 4 h of high flow. In contrast, SOD mRNA expression was increased only after 4 h of high flow. Neither gene is induced by exposure to low flow. On the basis of these data, we concluded that ecNOS and SOD mRNA expression is regulated by flow in porcine coronary arterioles. In addition, we concluded that a threshold level of flow and shear stress must be sustained to elicit the upregulation of ecNOS and SOD mRNA expression.
gene expression; reverse transcription polymerase chain reaction; complementary deoxyribonucleic acid synthesis; endothelium-derived relaxing factor; superoxide dismutase
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INTRODUCTION |
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Top
Abstract
Introduction
Methods
Results
Discussion
References
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ENDOTHELIAL CELL nitric oxide synthase (ecNOS) catalyzes the conversion of L-arginine to nitric oxide and citrulline. The nitric oxide produced by this reaction can dilate blood vessels by stimulating guanylyl cyclase and increasing cGMP in vascular smooth muscle cells. Recently, it has been shown that nitric oxide-dependent vasodilation is enhanced in coronary arteries and arterioles isolated from exercise-trained animals (18, 28). The mechanism for this training adaptation is not completely understood; however, it appears to involve an increased production of nitric oxide, because the adaptation can be blocked or attenuated by arginine analogs (18, 28). This speculation is supported by the finding that nitrite production in large coronary arteries and coronary resistance vessels is greater in tissue isolated from exercise-trained dogs than in that from sedentary controls (24).
It has been hypothesized that the increased nitric oxide production associated with training is mediated by an increased expression of the gene coding for ecNOS (24). Indeed, ecNOS mRNA content is upregulated by exercise training in the canine aorta (24) and in coronary resistance arteries isolated from pigs (29). The mediator of the exercise-induced increase in ecNOS mRNA expression is not known; however, two lines of evidence suggest that an increase in shear stress may provide the signal. First, ecNOS mRNA content is upregulated in cultured endothelial cells exposed to shear stress (20-22, 27, 30). Second, endothelium-dependent vasodilation and ecNOS mRNA expression are greater in arteries of dogs and rats with increased blood flow produced by arteriovenous fistulas (14, 19).
In addition to increased nitric oxide production, a reduction in the
rate of nitric oxide degradation could contribute to the enhanced
nitric oxide-dependent vasodilation in coronary arteries isolated from
exercise-trained animals. A primary mechanism of nitric oxide
degradation in endothelial cells is its rapid interaction with
superoxide anion (O
2·). Therefore, an important mechanism to prolong the biological half-life of nitric
oxide is to scavenge O2· (5, 6).
The Cu/Zn-dependent isoform of superoxide dismutase (SOD) provides the
primary enzymatic mechanism of O2· scavenging in endothelial cells (1, 3, 7, 26); therefore, an
upregulation of SOD expression could be complementary to the increase
in ecNOS and further enhance nitric oxide-dependent vasodilation. This
speculation is supported by the finding that nitric oxide-mediated dilation of coronary arteries is attenuated by inhibitors of SOD (15,
23).
Although the responses of endothelial SOD to exercise training have not been reported, it is known that exposure of cultured endothelial cells to shear stress upregulates SOD mRNA expression (7). Thus it is conceivable that shear stress in coronary arterioles is an important factor contributing to the regulation of ecNOS and SOD gene expression in a coordinated fashion to enhance endothelial function.
The purpose of this study was to test the hypothesis that increased flow and shear stress augment the expression of ecNOS mRNA in single coronary arterioles. In addition, we tested the hypothesis that SOD mRNA expression is induced by flow. The isolated perfused microvessel technique was used to allow control of all variables except vessel diameter, which was measured. Consequently, the only difference among arterioles was the amount of intraluminal flow and shear stress to which they were exposed during the experiment.
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METHODS |
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Top
Abstract
Introduction
Methods
Results
Discussion
References
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Experimental animals. Before this study was initiated, approval was received from the Animal Care and Use Committee at the University of Missouri. The experimental animals were immature male and female farm pigs (Landrace-Duroc; n = 6). The pigs were 2 mo of age and weighed 8-9 kg. All of the pigs were housed in the animal care facility in the Department of Veterinary Biomedical Sciences in a room maintained at 20-23°C with a 12:12-h light-dark cycle.
Isolation and cannulation of coronary arterioles. On the morning of an experiment, pigs were sedated with ketamine (35 mg/kg iv) and Rompun (2.25 mg/kg im) and anesthetized with Pentothal Sodium (10 mg/kg iv). The hearts were rapidly removed and placed in cold physiological saline solution (4°C). Single coronary arterioles (ID 100-160 µm; pressurized) in the region of the left anterior descending coronary artery were then dissected free of the surrounding myocardium under a dissection microscope. The arterioles were transferred to a Plexiglas chamber containing MOPS-buffered physiological saline solution containing (in mM) 145.0 NaCl, 4.7 KCl, 2.0 CaCl2, 1.17 MgSO4, 1.2 NaH2PO4, 5.0 glucose, 2.0 pyruvate, 0.02 EDTA, and 3.0 MOPS, pH 7.4, and 1 g/100 ml bovine serum albumin. This solution was equilibrated with room air. The arterioles were mounted on glass micropipettes of matched tip resistance and stretched to approximately the length measured in the myocardium.
Each glass pipette was connected to an independent hydrostatic pressure reservoir. The height of each reservoir could be adjusted to set the intraluminal pressure of the arteriole. By changing the height of each reservoir in equal but opposite directions, we could create a pressure difference across the length of the vessel while the mean intraluminal pressure was held constant (9).Exposure of arterioles to constant intraluminal flow. Each arteriole was pressurized to 60 cmH2O. Leaks were detected by pressurizing the arteriole and verifying that intraluminal pressure remained constant when the valves to the reservoirs were closed. All arterioles that leaked were discarded. Once the arteriole was determined to be leak free, a pressure difference was established across the vessel. The arteriole was then exposed to either high flow (7.52 ± 0.22 µl/min) or low flow (0.84 ± 0.05 µl/min) for 2 or 4 h. Flow rate was measured with an in-line flowmeter (Omega). The high-flow conditions were selected on the basis of previously published data indicating that flow of this magnitude elicits maximal flow-induced dilation in coronary arterioles (10, 16, 17). The low-flow conditions were selected because flow rates in this range are on the linear portion of the diameter-flow curve for coronary arterioles and are well below the shear stress values established for maximal flow-induced dilation (10, 16, 17).
Mean shear stress (
) was calculated using the equation
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is the viscosity at 37°C (0.71 cP), 
is the
volumetric flow rate, and r is the
vessel radius recorded during the experiment. The cannulated arteriole
was viewed through an inverted microscope (Nikon Diaphot TND) coupled
to a video camera (Panasonic WV 1500x) and TV monitor (Panasonic
TR930B). Vessel diameter was continuously recorded with a video
tracking device (Microcirculation Research Institute, Texas A&M
University, College Station, TX). The physiological saline solution
bathing the arteriole was maintained at 37°C and changed every 20 min. At the end of the 2- or 4-h protocol, the arteriole was removed
from the pipettes and the ends of the arteriole that had been tied onto
the pipettes were removed. Care was taken not to allow the arteriole to
collapse when the vessel was removed from the pipettes because
excessive mechanical manipulation appeared to hinder detection of mRNA
(data not shown). Each arteriole was then placed in a separate
RNase-free microcentrifuge tube and quick frozen at 
80°C
until the time of RNA isolation.
No-flow controls.
To further assess the role of flow in the regulation of ecNOS and SOD
mRNA expression, coronary arterioles were isolated as described in
Isolation and cannulation of coronary
arterioles. Each arteriole was placed in the same
Lucite chamber with a high- or low-flow arteriole but was not mounted
or perfused during the 4-h experimental protocol. Consequently, these
arterioles were exposed to the same bath conditions as the high- and
low-flow arterioles but were not exposed to intraluminal flow (no flow; n = 6). At the end of the 4-h
protocol, the arterioles were placed in separate RNase-free
microcentrifuge tubes and quick frozen at 80°C until the
time of RNA isolation.
Isolation of mRNA. Poly(A)+ RNA was isolated as described previously (29). In brief, each arteriole was homogenized in 50 µl of LiCl buffer [100 mM Tris · HCl (pH 8.0), 500 mM LiCl, 10 mM EDTA (pH 8.0), 1% lithium dodecyl sulfate, and 5 mM dithiothreitol (DTT)]. The lysate was then spun for 60 s in a microcentrifuge (14,000 g) to remove any insoluble material. Poly(A)+ RNA was isolated from the crude lysate using paramagnetic oligo(dT) polystyrene beads [Dynabeads Oligo(dT)25, Dynal].
First-strand cDNA synthesis. First-strand cDNA synthesis was performed in a 20-µl volume as described previously (29). Specifically, 10 µl of Poly(A)+ RNA, 1 µl of oligo (dT)12-18 (0.5 µg/µl), and 40 units of RNase inhibitor (40 U/µl; Boehringer Mannheim) were mixed gently, incubated for 10 min at 70°C, and placed on ice. Two microliters of PCR buffer [200 mM Tris · HCl (pH 8.4) and 500 mM KCl], 2 µl of 25 mM MgCl2, 1 µl of 10 mM dNTP, and 2 µl of 0.1 M DTT were then added to each sample. The samples were mixed, briefly spun in a microcentrifuge (14,000 g), and incubated in a 42°C water bath for 5 min. At the end of the 5-min incubation, 200 units of reverse transcriptase (200 U/µl; SuperScript II; Life Technologies, Gaithersburg, MD) were added to each sample and the reaction was allowed to proceed for 50 min at 42°C. The reaction was terminated by incubating each sample in a 70° water bath for 15 min. The RNA template was digested by adding 2 units of RNase H (Life Technologies) and incubating the mixture in a 37° water bath for 20 min.
PCR. Five microliters of the reverse-transcribed cDNA sample were used to perform a PCR reaction using primers specific for ecNOS and SOD. The sequences of the ecNOS have been published previously (29) and were as follows: ecNOS sense, 5'-GTG TTT GGC CGA GTC CTC ACC-3'; and ecNOS antisense, 5'-CTC CTG CAA GGA AAA GCT CTG-3'. The SOD primers were based on the reported human sequence for SOD (25) and were as follows: SOD sense, 5'-GTA ATG GAC CAG TGA AGG TGT G-3'; and SOD antisense, 5'-CAA TTA CAC CAC AAG CCA AAC G-3'. The PCR reaction was standardized by coamplifying ecNOS or SOD with glyceraldehyde-3-phosphate dehydrogenase (GAPDH). GAPDH is a constitutively expressed gene that is not altered by exposure to shear stress (4). The GAPDH primers (Stratagene) were 24 nucleotides in length with the following sequence: sense, 5'- CCA CCC ATG GCA AAT TCC ATG GCA-3'; and antisense, 5'-TCT AGA CGG CAG GTC AGG TCC ACC-3'. The PCR reaction for ecNOS was initiated with a denaturation step at 94°C (5 min) and an annealing step at 60°C (5 min). This was followed by 35 cycles at 72°C (2 min), 94°C (1 min), and 60°C (1 min). The PCR reaction was terminated with a final elongation step at 72°C (10 min). The PCR reaction conditions for SOD were identical to those used for ecNOS with the exception of the annealing temperature, which was 63°C. The PCR-amplified products were electrophoresed on a 1.5% agarose gel and visualized with ethidium bromide staining.
Semiquantitative PCR.
Relative differences in ecNOS and SOD mRNA expression in vessels
exposed to high-flow, low-flow, or no-flow conditions were assessed
using a semiquantitative PCR reaction (13, 29). Specifically, 5 µl of
the reverse-transcribed cDNA were used to perform a PCR reaction
that was spiked with 10 µCi of
[
-32P]dCTP (3,000 Ci/mmol) and terminated after 25 rounds to ensure that the reaction was
within the linear range for the ecNOS, SOD, and GAPDH primer
sets. The PCR-amplified products were electrophoresed on a 1.5%
agarose gel, and the ecNOS, SOD, and GAPDH bands were excised,
dissolved separately in 1 ml QX1 solution (Qiagen), and mixed with 10 ml of scintillation fluid. The samples were counted for 1 min in a
liquid scintillation counter (Packard 1600CA), and ecNOS-to-GAPDH and
SOD-to-GAPDH ratios were determined for each coronary arteriole.
Data analysis. All values are means ± SE. Between-group differences in ecNOS-to-GAPDH ratio, SOD-to-GAPDH ratio, and shear stress were assessed using one-way ANOVA or Student's t-tests where appropriate. Within- and between-group differences in vessel diameter were assessed using two-way ANOVA with repeated measures on one factor.
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RESULTS |
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Top
Abstract
Introduction
Methods
Results
Discussion
References
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Vessel diameter and shear stress.
The effect of 4 h of low or high flow on the diameter of coronary
arterioles is shown in Fig. 1. Statistical
analyses revealed no significant within- or between-group differences
in vessel diameter during the 4-h protocol. Mean shear stress over the
4-h protocol was significantly greater in the high-flow vessels than in
the low-flow vessels (Fig. 2).
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ecNOS mRNA expression.
The effect of 4 h of flow on the expression of ecNOS and GAPDH in
single coronary arterioles is shown in Fig.
3. GAPDH levels were similar in vessels
exposed to low- or high-flow conditions. In contrast, ecNOS mRNA levels
were greater in coronary arterioles exposed to high flow than in those
exposed to low or no flow. Semiquantitative PCR revealed
that the ecNOS-to-GAPDH ratio for the high-flow arterioles was
significantly greater than that for the low-flow and no-flow arterioles
at 2 and 4 h (Fig. 4;
P = 0.012).
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SOD mRNA expression.
The effect of flow on SOD mRNA expression in single coronary arterioles
is shown in Fig. 5. The SOD-to-GAPDH ratio
for the high-flow arterioles at 4 h was greater than those for the
low-flow and no-flow arterioles (P = 0.059).
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DISCUSSION |
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Top
Abstract
Introduction
Methods
Results
Discussion
References
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The purpose of this study was to test the hypothesis that ecNOS mRNA expression is increased as flow increases through coronary arterioles. In addition, we tested the hypothesis that SOD mRNA expression is induced by flow. Coronary arterioles were studied because they represent a primary site of resistance in the coronary circulation (2). The isolated perfused microvessel technique was used to allow control of all variables that determine shear except vessel diameter, which was measured. Consequently, the only difference among arterioles was the amount of intraluminal flow and shear stress to which they were exposed.
The key finding of the study is that ecNOS mRNA expression was increased in coronary arterioles exposed to high-flow conditions for 2 or 4 h. In addition, the results suggest that SOD mRNA expression was increased by exposure to 4 h of high flow (P = 0.059). In contrast, neither gene was induced by low flow, indicating that a threshold level of flow and shear stress must be sustained to increase the expression of these genes in coronary arterioles. The functional significance of this study is that we were able to demonstrate an effect of shear stress on ecNOS and SOD expression in isolated coronary arterioles with shear stress in a range that has been shown to produce vigorous functional responses in isolated perfused microvessels (10, 16, 17). In addition, these data provide a meaningful link with cell culture studies indicating that ecNOS and SOD mRNA levels are induced by shear stresses similar in magnitude and duration to the conditions used in the coronary arterioles in this study (7, 22, 27, 30).
It has been shown previously that the capacity to increase coronary blood flow is increased by a program of endurance exercise training (11, 12). The improved ability to deliver blood to the heart is due, in part, to an enhanced ability to produce and release nitric oxide (18, 28). It has been hypothesized that the increased nitric oxide production in coronary resistance arteries is mediated by an upregulation of ecNOS mRNA (24, 29). Data collected in this study are consistent with the hypothesis that an important signal for the increase in ecNOS gene expression is increased flow and shear stress.
Nadaud et al. (19) reported that ecNOS gene expression was increased in rat aortas exposed to 6 wk of high flow produced by an arteriovenous fistula, a result similar to ours. These authors, however, did not measure flow or diameter in their rats. Consequently, the flow and shear stress that produced the changes are unknown. Also, in their in vivo model, neural-humoral mediators may have contributed to altered gene expression. In the present study, a 4-h protocol was used in which the only difference between resistance arteries was shear stress. The rapid increase in ecNOS gene expression in response to flow and shear stress observed in this study (Fig. 4) is in agreement with cell culture studies indicating that the increase in ecNOS mRNA expression occurs within hours of the onset of flow (21, 22, 27, 30).
In response to exposure to flow that produces maximal flow-induced dilation (i.e., high flow), ecNOS mRNA expression was enhanced (Fig. 3), whereas GAPDH mRNA expression was unchanged. The ecNOS-to-GAPDH ratio was significantly greater in the high-flow vessels (Fig. 4). It is interesting that the magnitude of increase in mRNA expression was similar to the increase previously reported in coronary resistance arteries isolated from exercise-trained pigs (29). These data support the speculation that increased ecNOS mRNA and protein expression associated with training is mediated, at least in part, by an increase in shear stress.
The mechanism by which an increase in flow and shear stress is transduced into an increase in ecNOS gene expression is not known. Nadaud et al. (19) speculated that the induction of ecNOS in aortic tissue was mediated by an increased rate of transcription via stimulation of a shear stress response element located within the promoter region of the ecNOS gene. Data obtained from cell culture studies support this notion, because endothelial cells exposed to shear stress exhibit an increase in ecNOS gene expression that is blocked by coincubation with actinomycin D (27). It is possible that similar transduction mechanisms were involved in these coronary arterioles; however, our results do not allow us to make conclusions about how increased shear stress produced altered ecNOS mRNA expression.
The increased expression of SOD mRNA in response to high flow is in agreement with previously published data indicating that SOD mRNA expression is increased by shear stress in cultured endothelial cells (7). In addition, it is likely that the effects of flow are specific to the endothelial cells, because cell culture experiments have demonstrated that shear stress has no effect on SOD mRNA levels in vascular smooth muscle (7). Although the responses of endothelial SOD to exercise training have not been reported, it is conceivable that shear stress in coronary arterioles is an important factor contributing to the regulation of this gene and may contribute in a coordinated fashion with the increased ecNOS gene expression to enhance endothelial function.
The mechanism for the effect of flow on SOD mRNA expression is not
known; however, the promoter region of Cu/Zn SOD contains three copies
of a consensus sequence that interacts with nuclear factor-
B (8).
Inoue et al. (7) have proposed that this transcription factor may be
important in the flow-/shear-mediated increases in SOD mRNA expression
in cultured endothelial cells. Whether this transcription factor
contributes to increased expression of SOD in coronary arterioles
remains to be determined.
In conclusion, the results of this study indicate that increased ecNOS and SOD mRNA expression can be stimulated in coronary arterioles by an increase in intraluminal flow. Our results indicate that one signal for the upregulation of these genes in coronary arterioles exposed to increased flow is an increase in shear stress. The increased ecNOS and SOD mRNA content may contribute to the enhanced nitric oxide-dependent vasodilation and increased blood flow capacity associated with endurance exercise training. Further studies are required to determine the molecular mechanisms by which shear stress increases ecNOS and SOD gene expression in coronary arterioles.
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ACKNOWLEDGEMENTS |
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We thank Pam Thorne and Cathy Korte for expert assistance with this project.
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FOOTNOTES |
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This study was supported by National Heart, Lung, and Blood Institute Grant HL-52490 (to M. H. Laughlin) and by National Research Service Award HL-09739 (to C. R. Woodman).
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Address for reprint requests: C. R. Woodman, Dept. of Veterinary Biomedical Sciences, W108 Veterinary Medicine, 1600 E. Rollins, Univ. of Missouri, Columbia, MO 65211 (E-mail: woodmanc{at}missouri.edu).
Received 6 April 1998; accepted in final form 20 November 1998.
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Discussion
References
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  L. Ai, M. Rouhanizadeh, J. C. Wu, W. Takabe, H. Yu, M. Alavi, R. Li, Y. Chu, J. Miller, D. D. Heistad, et al. Shear stress influences spatial variations in vascular Mn-SOD expression: implication for LDL nitration Am J Physiol Cell Physiol, June 1, 2008; 294(6): C1576 - C1585. [Abstract] [Full Text] [PDF]
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 M. H. Laughlin, S. C. Newcomer, and S. B. Bender Importance of hemodynamic forces as signals for exercise-induced changes in endothelial cell phenotype J Appl Physiol, March 1, 2008; 104(3): 588 - 600. [Abstract] [Full Text] [PDF]
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 C. Yan, A. Huang, G. Kaley, and D. Sun Chronic high blood flow potentiates shear stress-induced release of NO in arteries of aged rats Am J Physiol Heart Circ Physiol, November 1, 2007; 293(5): H3105 - H3110. [Abstract] [Full Text] [PDF]
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S. C. Newcomer, U. A. Leuenberger, C. S. Hogeman, and D. N. Proctor Heterogeneous vasodilator responses of human limbs: influence of age and habitual endurance training Am J Physiol Heart Circ Physiol, July 1, 2005; 289(1): H308 - H315. [Abstract] [Full Text] [PDF]
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C. R. Woodman, E. M. Price, and M. H. Laughlin Shear stress induces eNOS mRNA expression and improves endothelium-dependent dilation in senescent soleus muscle feed arteries J Appl Physiol, March 1, 2005; 98(3): 940 - 946. [Abstract] [Full Text] [PDF]
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P. G. Lloyd, B. M. Prior, H. Li, H. T. Yang, and R. L. Terjung VEGF receptor antagonism blocks arteriogenesis, but only partially inhibits angiogenesis, in skeletal muscle of exercise-trained rats Am J Physiol Heart Circ Physiol, February 1, 2005; 288(2): H759 - H768. [Abstract] [Full Text] [PDF]
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J. D. Symons, Y. Hayashi, and J. L. Ensunsa Improved coronary vascular function evoked by high-intensity treadmill training is maintained in arteries exposed to ischemia and reperfusion J Appl Physiol, October 1, 2003; 95(4): 1638 - 1647. [Abstract] [Full Text] [PDF]
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J. Ma, C. I. Kahwaji, Z. Ni, N. D. Vaziri, and R. E. Purdy Effects of simulated microgravity on arterial nitric oxide synthase and nitrate and nitrite content J Appl Physiol, January 1, 2003; 94(1): 83 - 92. [Abstract] [Full Text] [PDF]
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M. H. Laughlin, L. J. Rubin, J. W. E. Rush, E. M. Price, W. G. Schrage, and C. R. Woodman Short-term training enhances endothelium-dependent dilation of coronary arteries, not arterioles J Appl Physiol, January 1, 2003; 94(1): 234 - 244. [Abstract] [Full Text] [PDF]
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C. R. Woodman, E. M. Price, and M. H. Laughlin Aging induces muscle-specific impairment of endothelium-dependent dilation in skeletal muscle feed arteries J Appl Physiol, November 1, 2002; 93(5): 1685 - 1690. [Abstract] [Full Text] [PDF]
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H. T. Yang, J. Ren, M. H. Laughlin, and R. L. Terjung Prior exercise training produces NO-dependent increases in collateral blood flow after acute arterial occlusion Am J Physiol Heart Circ Physiol, January 1, 2002; 282(1): H301 - H310. [Abstract] [Full Text] [PDF]
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C. R. Woodman, W. G. Schrage, J. W. E. Rush, C. A. Ray, E. M. Price, E. M. Hasser, and M. H. Laughlin Hindlimb unweighting decreases endothelium-dependent dilation and eNOS expression in soleus not gastrocnemius J Appl Physiol, September 1, 2001; 91(3): 1091 - 1098. [Abstract] [Full Text] [PDF]
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J. L. Tuttle, R. D. Nachreiner, A. S. Bhuller, K. W. Condict, B. A. Connors, B. P. Herring, M. C. Dalsing, and J. L. Unthank Shear level influences resistance artery remodeling: wall dimensions, cell density, and eNOS expression Am J Physiol Heart Circ Physiol, September 1, 2001; 281(3): H1380 - H1389. [Abstract] [Full Text] [PDF]
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L. R. Johnson, J. W. E. Rush, J. R. Turk, E. M. Price, and M. H. Laughlin Short-term exercise training increases ACh-induced relaxation and eNOS protein in porcine pulmonary arteries J Appl Physiol, March 1, 2001; 90(3): 1102 - 1110. [Abstract] [Full Text] [PDF]
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M. H. Laughlin, J. S. Pollock, J. F. Amann, M. L. Hollis, C. R. Woodman, and E. M. Price Training induces nonuniform increases in eNOS content along the coronary arterial tree J Appl Physiol, February 1, 2001; 90(2): 501 - 510. [Abstract] [Full Text] [PDF]
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J. W. E. Rush, M. H. Laughlin, C. R. Woodman, and E. M. Price SOD-1 expression in pig coronary arterioles is increased by exercise training Am J Physiol Heart Circ Physiol, November 1, 2000; 279(5): H2068 - H2076. [Abstract] [Full Text] [PDF]
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W. G. Schrage, C. R. Woodman, and M. H. Laughlin Hindlimb unweighting alters endothelium-dependent vasodilation and ecNOS expression in soleus arterioles J Appl Physiol, October 1, 2000; 89(4): 1483 - 1490. [Abstract] [Full Text] [PDF]
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 V. Hampl and J. Herget Role of Nitric Oxide in the Pathogenesis of Chronic Pulmonary Hypertension Physiol Rev, October 1, 2000; 80(4): 1337 - 1372. [Abstract] [Full Text] [PDF]
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 Z. Cai, J. Xin, D. M. Pollock, and J. S. Pollock Shear stress-mediated NO production in inner medullary collecting duct cells Am J Physiol Renal Physiol, August 1, 2000; 279(2): F270 - F274. [Abstract] [Full Text] [PDF]
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M. R. McCurdy, P. N. Colleran, J. Muller-Delp, and M. D. Delp Physiology of a Microgravity Environment: Selected Contribution: Effects of fiber composition and hindlimb unloading on the vasodilator properties of skeletal muscle arterioles J Appl Physiol, July 1, 2000; 89(1): 398 - 405. [Abstract] [Full Text] [PDF]
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L. R. Johnson, J. L. Parker, and M. H. Laughlin Chronic exercise training improves ACh-induced vasorelaxation in pulmonary arteries of pigs J Appl Physiol, February 1, 2000; 88(2): 443 - 451. [Abstract] [Full Text] [PDF]
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J. L. Jasperse, C. R. Woodman, E. M. Price, E. M. Hasser, and M. H. Laughlin Hindlimb unweighting decreases ecNOS gene expression and endothelium-dependent dilation in rat soleus feed arteries J Appl Physiol, October 1, 1999; 87(4): 1476 - 1482. [Abstract] [Full Text] [PDF]
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