Continuous in vivo perfusion of the postglomerular capillary network in superficial rat kidney cortex.

The experimental design of many micropuncture studies requires clhanges in the perittll)lllar environrment. C'lassically, these clhanges are incluced by systemic infusion of suitable solutions. This technique lhas significant slhortcomings due to the tunavoidlable modification in the composition of the glomertular filtrate an(i to clhanges in the rate of glomerular filtration. Various approachies are being uisedl to circtumvent tile effect on glomerular filtration rate (GFR), but notlling can be (lone, under stuclh circumstances, to maintain constant the composition of the filtrate. Only in Necturus, because of its dual renal blood supply, is it possible to vary indlependently tile composition of the fluid reaciling tile two sicles of the tutbular membrane. Tile findings suggesting a possible correlation between the transport capacity of the proximal tubtular membrane and extratubular events(l,2), stimulated our searci for a metliod whiclh wouldl allow selective monitoring of fluid passing tlhrotugh the peritubular capillaries of the mammalian kidney. We decided, tllere-fore, to attempt to perfuse (lirectly anci contintuously the postglomerular capillary network on tile kidney surface in vivo(3). Fr6mter(4) and Rumrich and Ullrich(5) (leveloped indlependlently a nearly identical technique. A precedent in tllis field was established, liowever, in 1965 by Leciene and M\orel(6) wl1o performed single boltis injections of fluid into the peritubular capillaries of hamsters. The anatomy of tile vascular bed of the rat kidney seemed suited for our purposes. As sliown initially by standlard fixation and staining methods(7), confirmed more recently