AJP - Renal Physiology, Vol 265, Issue 2 309-F315, Copyright © 1993 by American Physiological Society
Endothelial modulation of renal interlobar arteries from pregnant rats
K. C. Griggs, K. P. Conrad, K. Mackey and M. K. McLaughlin
Department of Obstetrics and Gynecology, University of Vermont, Burlington 05405.
The purpose of this study was to determine whether there are gestational
effects on 1) the response of resistance arteries from the renal
vasculature to phenylephrine and 2) the endothelial modulation of these
arteries. Interlobar arteries (200-300 microns ID) were isolated from the
kidneys of virgin and pregnant rats at 18-20 days of gestation (term, 22
+/- 1 days) and studied in a pressurized arteriograph system. Intact
arteries from virgin and pregnant rats did not differ in sensitivity to
phenylephrine. Arteries without endothelium from both groups were more
sensitive to phenylephrine than arteries with endothelium. Sensitivity was
increased 3.4-fold by endothelial removal in arteries from virgin rats and
1.5-fold in the pregnant group. Concentration-response relationships to
phenylephrine were determined in arteries with endothelium and then
repeated in the presence of 2.5 x 10(-4) M N omega-nitro-L-arginine
(L-NNA), an inhibitor of nitric oxide synthase. All arteries were more
sensitive to phenylephrine in the presence of L-NNA, with an average
increase of 3.2-fold for the arteries from virgin rats and 1.6-fold from
pregnant rats. These results indicate that the increased sensitivity to
phenylephrine is primarily due to elimination of endothelium-derived
relaxing factor (EDRF) and that basal EDRF activity is decreased during
late gestation. To determine whether stimulated endothelium-dependent
relaxation is enhanced in pregnancy, arteries with endothelium were
constricted with phenylephrine to 50% of their maximum and relaxed to
increasing concentrations of methacholine.(ABSTRACT TRUNCATED AT 250 WORDS)
