AJP - Heart and Circulatory Physiology, Vol 258, Issue 1 165-H172, Copyright © 1990 by American Physiological Society
Postunclipping renal blood flow in one-kidney, one-clip hypertensive rats
Y. H. Ma and E. W. Dunham
Department of Pharmacology, Medical School, University of Minnesota, Minneapolis 55455.
Removal of the arterial clip (unclipping) in one-kidney, one-clip (1K, 1C)
Goldblatt hypertensive rats causes rapid return of mean arterial pressure
(MAP) to normotensive levels. An extracorporeal circulation was established
between the renal and jugular veins to evaluate the influence of unclipping
on renal blood flow (RBF) in Inactin-anesthetized 1K, 1C rats. MAP in rats
with the extracorporeal circulation was 182 +/- 5 mmHg before unclipping or
sham operation. MAP decreased to 113 +/- 4 mmHg within 2 h after unclipping
compared with 169 +/- 13 mmHg in sham-unclipped rats. RBF increased by 2.8
ml.min-1.g-1 from a basal level of 3.8 +/- 0.3 after unclipping and was
maintained approximately 40% above the basal level for 2 h, although renal
vascular resistance was 94% greater than in uninephrectomized control rats.
Heart rate did not change in either unclipped or sham-operated rats.
Indomethacin (7 mg/kg) did not affect unclipping-induced changes in MAP,
RBF, or urine output; however heart rate decreased immediately after
unclipping and remained approximately 25-35 beats/min below control levels
for the 2-h observation period. In rats lacking the extracorporeal circuit,
MAP decreased (P less than 0.005) and heart rate increased (P less than
0.05) in response to unclipping. Nevertheless, unclipping-induced
tachycardia was significantly less than that caused by nitroprusside
infusions causing similar decrements in MAP. The results suggest that the
sustained increment in RBF after unclipping in chronic, established 1K, 1C
hypertension may be associated with postunclipping hypotension and
diuresis, that blockade of prostaglandin synthesis may unmask
unclipping-induced bradycardia, and that prostaglandins are not essential
for postunclipping changes in renal hemodynamics.
