A servo-system for constant pressure perfusion of the isolated rat kidney

A technical difficulty in perfusion of the isolated rat kidney has been the regulation of perfusion pressure. Since perfusion pressure is an important determinant of renal function, this parameter should be well regulated for experimental consistency. A servo-system is described that uses analog circuitry to calculate and maintain the cannula tip pressure for perfusion of the isolated kidney. The system is sufficiently responsive to maintain a constant perfusion pressure during the rapid changes in renal resistance caused by addition of angiotensin II or epinephrine to the perfusate. Analog outputs are provided for the recording of perfusion flow rate, perfusion pressure, and renal resistance.