Effects of endothelium-derived nitric oxide on renal hemodynamics and function in the sheep fetus.
We investigated the effects of the endothelium-derived nitric oxide system on renal hemodynamics and function during the 3rd trimester in a chronically catheterized fetal sheep preparation. Acetylcholine caused a significant decrease in renal vascular resistance (60% of the baseline value) as compared with aortic constriction (142% of the baseline value). The effects of acetylcholine could be blocked by prior administration of N omega-nitro-L-arginine (renal vascular resistance = 102% of baseline). Sodium nitroprusside also caused a significant drop in renal vascular resistance (63% of baseline), but this could not be blocked by N omega-nitro-L-arginine (77% of baseline). Infusion of N omega-nitro-L-arginine with blood pressure maintained at a constant level resulted in a significant increase in renal vascular resistance (148% of the baseline value) as compared with saline alone (94% of baseline). Glomerular filtration rate increased after saline infusion (156% of the baseline value), but this increase was blocked by N omega-nitro-L-arginine (87% of baseline). Sodium excretion also increased (340%), and this increase was blunted by N omega-nitro-L-arginine (235%). We conclude that basal production of endothelium-derived nitric oxide results in ongoing renal vasodilation in 3rd-trimester fetal sheep, maintaining baseline renal blood flow. The endothelium-derived nitric oxide system can also be stimulated to an increased level of activity, and its blockade partially prevents the homeostatic response of the fetus to volume and salt overload.
Bogaert
G A
GA
Department of Urology, University of California School of Medicine, San Francisco 94143-0738.
Kogan
B A
BA
Mevorach
R A
RA
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D004231:Diuresis / Q000187:drug effects / Q000502:physiology; D004730:Endothelium, Vascular / Q000502:physiology; D005260:Female; D005333:Fetus / Q000187:drug effects / Q000502:physiology*; D005919:Glomerular Filtration Rate / Q000187:drug effects / Q000502:physiology; D007668:Kidney / Q000187:drug effects / Q000502:physiology*; D009318:Natriuresis / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000502:physiology*; D019335:Nitroarginine; D009599:Nitroprusside / Q000494:pharmacology; D011247:Pregnancy; D012079:Renal Circulation / Q000187:drug effects / Q000502:physiology*; D012756:Sheep; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
D009599:Nitroprusside; D019335:Nitroarginine; D009569:Nitric Oxide; D001120:Arginine