AJP - Heart and Circulatory Physiology, Vol 246, Issue 5 702-H709, Copyright © 1984 by American Physiological Society
Instantaneous renal arterial pressure-flow relations in anesthetized dogs
W. Ehrlich, R. W. Baer, B. B. Paidipaty and R. Randazzo
Instantaneous renal arterial pressure-flow (P/ Qra ) relations were
investigated in 11 anesthetized dogs using the nonpulsatile fall in aortic
pressure and renal arterial flow ( Qra ) during cardiac arrest caused by
vagal stimulation. We found that P/ Qra relations were linear with an
extrapolated zero flow intercept (Ped, effective downstream pressure) of
20.8 +/- 1.9 mmHg and the reciprocal of the slope (Ra, arterial resistance)
of 0.6 +/- 0.04 mm Hg X ml-1 X min. These values are markedly lower than
the values found in similar experiments in coronary and femoral arteries.
Raising renal venous pressure (5 dogs) decreased Qra and elevated Ra and
Ped in the ipsilateral renal artery while decreasing Qra and elevating Ra
but not Ped in the contralateral renal artery. Carotid artery occlusion (6
dogs) decreased Qra and elevated Ra and Ped. Alpha-Adrenergic blockade (4
dogs) lowered Ped and Ra. Arterial resistance seems to be more important
for change in P/Q relations in the renal arterial bed than it is in other
arterial beds investigated so far. We suggest that the effective downstream
pressure to renal arterial flow is downstream from the glomerular
capillaries. The location of the "vascular waterfall " phenomenon appears
to be between the intrarenal veins and the veins outside the capsule.
