Glomerular filtration rate as a function of the net transcapillary hydrostatic pressure

Abstract

This report briefly reviews two current hypotheses of glomerular dynamics. Each predicts a fundamentally different effect of net hydrostatic pressure across the glomerular capillary wall ( Δ P ) and glomerular plasma flow on glomerular filtration rate (GFR). Filtration pressure equilibrium, in which the net ultrafiltration pressure declines to zero before the end of the capillary, predicts that GFR is insensitive to changes in Δ P . In contrast, filtration pressure disequilibrium, in which the net ultrafiltration pressure favors filtration along the entire capillary, predicts that GFR is dependent on changes in Δ P . In the dog, a species characterized by filtration disequilibrium, few studies have addressed quantitatively either the theoretical or experimental description of the relationship between GFR and Δ P . To evaluate the expected relationship between Δ P and GFR we used computer analysis of a mathematical model of ultrafiltration. The values obtained were compared to experimental data from the literature. This analysis provides a basis for understanding the hemodynamic mechanism by which a drug or hormone alters GFR under conditions of filtration disequilibrium.