Pressure induced changes of renal flow resistance in the dog kidney in situ.

Abstract

In mongrel dogs renal venous blood flow was continuously measured by means of an electromagnetic flowmeter, and the pressure in the renal artery was monitored by a Statham transducer. Short lasting diastolic elevations of arterial pressure (pressure steps) were induced by arterial counterpulsation (diastolic augmentation), i.e. rapid pumping of a variable blood volume into the aorta. Initially, after the induced steep rise of pressure, mean arterial pressure falls, attaining its minimum after about 10 sec, and reaching the control value after about 20 sec. The corresponding renal blood flow decreases in two phases. Following an initial minor and short lasting fall which begins 0.5–1 sec after the pressure step and reaches its minimum after 1.5 sec, a second, larger diminuation of flow occurred which depended on the magnitude of the pressure step. The minimum of flow was reached about 10 sec after the induced pressure rise, subsequently the control value was reattained within 20 sec. The changes of flow reflect pressure induced biphasic changes of flow resistance.