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Abstract:
A network thermodynamic model was utilized to assess similarities and dissimilarities in the predicted response of human, rat, and dog glomeruli to change in the independent variables regulating glomerular filtration. The analysis in rat and dog employed basal values reported in the micropuncture literature. The analysis in man was based on a calculated total nephron vascular resistance (Rt) of 1.2 X 10(10) dyne sec cm-5 with a range of pre- (Ra) and postglomerular (Re) resistances and capillary hydraulic conductivities (Kf) that would provide a nephron blood flow (GBF) of approximately 550 nl/min and single nephron filtration rate (SNGFR) of approximately 65 nl/min. The maximal putative value for Ra/Re in man was approximately 1.1, a ratio demanding a Kf greater than 20 nl/min mm Hg to obtain the required SNGFR. Solitary changes in Ra and Re, glomerular capillary resistance, proximal tubule pressure, serum protein concentration, total vascular resistance, and Kf were induced and the resultant effect on SNGFR was examined in the three species. The relationship between changes in individual resistances, glomerular blood flow, glomerular filtration, and glomerular capillary pressure also was assessed. The patterns of response in man and dog, determined by the model, were remarkably similar and distinct from those of the rat in many regards. Except when the maximal possible Ra/Re ratio is assumed for man, filtration pressure equilibrium was not found; plasma flow dependence of SNGFR was not evident in rat, dog, or man. The differences in SNGFR control predicted for the rat, on the one hand, and dog and man on the other may have distinct physiologic significance.