AJP - Regulatory, Integrative and Comparative Physiology, Vol 235, Issue 1 64-R75, Copyright © 1978 by American Physiological Society
Humoral and mechanical factors modulating neural input to the renal vasculature
D. E. Carlson and L. P. Schramm
The velocity and magnitude of neurally elicited renal vasoconstrictions
decrease with reduction of renal arterial pressure. We investigated the
relative roles of humoral and mechanical factors in this decrease. Cats
were anesthetized with chloralose. Renal arterial pressure was controlled
with an aortic cuff. Vasoconstrictions were elicited by electrical
stimulation of the renal nerves until renal vascular resistance stabilized.
Renal blood flow autoregulation was maintained during stimulation.
Competitive blockade of angiotensin II did not affect the decrease in renal
vascular responsiveness to neural input at reduced renal arterial pressure.
A mathematical model suggested that a major portion of the decrease in the
velocity of vasoconstrictions was a mechanical consequence of
autoregulatory vasodilation. However, the model was only able to account
for the experimental findings after the blockade of prostaglandin
synthesis, and this blockade significantly increased the velocity of
vasoconstrictions at renal arterial pressures of 75 Torr or below. These
results suggested that prostaglandins as well as mechanical factors played
a role in the autoregulatory decrease in responsiveness to sympathetic
input.
