PRESSURE NATRIURESIS IN EXPERIMENTAL GLOMERUIO NEPHRITIS

To examine possible adaptive mechanisms involved in the maintenance of glomerular filtration and sodium balance in glomerulonephritis, an in situ perfused kidney was compared in 7 normal mongrels (N) and in 6 mongrels 2 to 4 months following the production of mild anti glomerular basement membrane nephritis (GN). The left kidney was perfused via a carotid-renal artery pump at systemic pressure levels and then at an elevated pressure. The average mean systemic pressure was higher in GN (140 mm Hg) than in N (121 mm Hg). Filtration rates (GFR) and renal plasma flows (RPF) were similar, averaging 17.3 and 88 ml/min in GN and 18.6 and 70.3 ml/min in N. When perfusion pressure was elevated to 195 mm Hg mean sodium excretion more than doubled in GN and in N while GFR and RPF decreased by 30% in GN and remained constant in N. The data demonstrate that pressure natriuresis occurs in GN as well as in N and that the GN kidney responds to increased perfusion pressure with exaggerated vasoconstriction as compared to N which autoregulates. The excessive vasoconstrictor response of the GN kidney may be revealing an adaptive vaso-dilatation which occurs as a mechanism for the maintenance of renal perfusion and sodium homeostasis.