RENAL VASCULAR AND SYMPATHETIC-NERVE RESPONSES TO HYPOTENSION INDUCEDBY PLATELET-ACTIVATING-FACTOR IN ANESTHETIZED DOGS

This experiment was designed to determine renal sympathetic and renal vascular responses to platelet-activating factor (PAF)-induced hypoten sion in anesthetized dogs with and without systemic baroreceptor dener vation. The left kidney was perfused at a constant flow, and renal per fusion pressure and efferent left renal sympathetic nerve activity wer e measured simultaneously. Intrarenal injection of PAF (1.25-5.0x10(-2 ) mu g/kg, n=6) produced a dose-dependent increase in renal perfusion pressure without any change in systemic blood pressure. An intravenous injection of PAF (10 mu g/kg) to intact animals (n=7) caused an initi al increase in renal nerve activity (157+/-14%) followed by a gradual reduction below baseline (72+/-7%) with concomitant systemic hypotensi on (from 116+/-7 to 46+/-6 mmHg). Renal perfusion pressure increased s ignificantly from 84+/-2 to 161+/-33 mmHg concomitant with an increase in renal nerve activity at 1 min and was maintained at this elevated level throughout the experiment. Similar responses of renal nerve acti vity and renal perfusion pressure were found in animals with complete systemic baroreceptor denervation (n=7). These results suggest that re nal vascular response during PAF-induced hypotension may presumably be mediated by a direct vasoconstrictor effect of PAF on the renal vascu lature and that baroreceptor reflex is not involved in either renal sy mpathetic or renal vascular changes.