Periodic changes in blood flow in the in vivo rat kidney

The frequency response of the blood flow through the rat kidney in vivo has been studied. A piston controlled by a random-signal generator compressed the abdominal aorta proximal to the renal artery eliciting stochastical arterial pressure changes of an amplitude of less than or equal to 5 mm Hg. This small amplitude allowed to study the system under physiological conditions. In accord with earlier results from isolated kidneys pressure induced maxima of flow resistance were found at 0.005 Hz and at 0.1 Hz, thus demonstrating that in vivo humoral and/or nervous factors do not significantly alter the renal vascular response to changes of arterial pressure.