AJP - Heart and Circulatory Physiology, Vol 251, Issue 5 976-H983, Copyright © 1986 by American Physiological Society
Altered aortic reactivity and lowered blood pressure associated with high calcium intake
R. D. Bukoski and D. A. McCarron
The hypothesis that dietary calcium (dCa) alters functional properties of
aortic smooth muscle in the spontaneously hypertensive rat (SHR) was
tested. At 6 wk of age, Wistar Kyoto (WKY) and (SHR) rats were placed on a
control diet containing 1% Ca. The experimental SHR group received a
2%-calcium diet. After an average of either 8 or 15 wk on the diets (WOD),
aortic rings were prepared for measurement of passive elastic properties
and isometric force development. Differences in blood pressure (BP) were
not apparent until after 8 WOD when the BP of SHRs on 2% dCa were 10-15
mmHg lower than SHRs on 1% dCa (P less than 0.05). After 8 WOD, when the BP
effect first emerged, no significant differences in aortic properties were
observed between the SHR groups. However, after 15 WOD, aortas of SHRs on
2% dCa were more compliant than those of SHRs on 1% dCa and between 8 and
15 WOD the sensitivity to KCl decreased in aortas from the WKY group and
the SHRs on 2% dCa, but not the SHR-1% dCa group (mean effective dose went
from 14.4 +/- 0.4 to 18.5 +/- 0.9 mM for WKY and from 13.6 +/- 0.6 to 17.1
+/- 1.2 mM for SHRs on 2% dCa, P less than 0.05). In addition, between 8
and 15 WOD, a significant decrease in response to a calcium (Ca2+)
challenge after removal of K+ and Ca2+ occurred in aortas of the SHRs on 2%
dCa, but not in the control diet groups, indicating that a decrease in
aortic reactivity was present in the Ca2+-supplemented SHR.(ABSTRACT
TRUNCATED AT 250 WORDS)
