Hemodynamic parameters of the isolated dog kidney as determined by a frequency response method

The isolated kidney of the dog was perfused with autologous blood through an oxygenator. Responses of arterial input pressure (PI), venous pressure (PV), and venous flow (UV) were measured during sinusoidal forcing of arterial inflow (UA) at 5 to 1,000 cpm superimposed on a steady-state flow level. Pre- (RA) and postglomerular (REV) resistances, and compliances of artery (CA) and glomeruli (CG) were estimated based on a network model and using the Bode diagram of gains PI/UA, UV/UA. The data were evaluated by the least square method with a digital computer. The mean values of the parameters normalized for the average weight of the kidney (64.5g) were: CA = 0.0027 ml/mmHg, CG = 0.088, RA = 0.45 mmHg . min/ml, and REV = 0.35. Mean arterial pressure (PA) and glomerular pressure (PG) were 111 and 50 mmHg, respectively. The regression lines of PG against PA were significantly different at high and low PA, this being taken as a manifestation of autoregulation of the renal circulation. PG values were less than those given by the classical study of Winton but close to those recently obtained on mutants rats with a direct puncture method by Brenner et al. It is concluded that the present study has given an experimental background with which we may continuously estimate, under more intact conditions, circulatory parameter values by monitoring pressures and flows which respond to external perturbations.