Effect of ouabain on renin secretion in anaesthetized dogs

1. Pentobarbitone anaesthetized dogs were used to study the effects on renin secretion of ureteral occlusion and partial aortic clamping before and after intrarenal arterial administration of ouabain.2. Arterial plasma renin activity (A renin) and renal venous minus arterial plasma renin activity (RV-A renin) were both increased by either ureteral occlusion during mannitol diuresis or partial aortic clamping to reduce renal perfusion pressure. Intrarenal arterial ouabain administration blunted or abolished the effects of these manoeuvres on A and RV-A renins.3. The observations are not consistent with the hypothesis that renin secretion is uniquely controlled by afferent arteriolar transmural pressure. Both ureteral occlusion and aortic clamping reduce this pressure and increase renin secretion, yet evidence presented herein suggests that ouabain, which also decreases this pressure, decreases renin secretion.4. The observations are consistent with the hypothesis that renin secretion is controlled by tubular fluid flow and/or composition in the region of macula densa cells. Possibly changes in flow and/or composition are detected as changes in macula densa intracellular sodium concentration.