Filtration dynamics in dogs: glomerular capillary pressure

Hydrostatic pressure in the glomerular capillaries, the primary driving force for glomerular ultrafiltration, is directly measurable only in those species with glomeruli present on the capsular surface of the kidney. Accordingly, this crucial measurement must be made indirectly in species not so endowed, such as the dog. Several different methods have been utilized in the dog; unfortunately each is indirect. This review deals with an assessment of the following methods for the determination of glomerular capillary pressure in dogs: a) reduction of arterial pressure method; b) ureteral occlusion method; c) the Winton or venous occlusion method; d) fraction of arterial pressure method; e) back calculation from forces opposing filtration; f) sieving method; and g) single nephron occlusion of the Gertz stop-flow method. Recent studies in the dog, utilizing single nephron occlusion techniques, provide estimates of glomerular capillary pressures of approximately 60 mn Hg in the autoregulatory range of blood pressure.