1. Plasma renin concentration is significantly higher in the subcapsular venous outflow, which drains the superficial cortex, than in the deep venous outflow, which drains the inner half of the cortex and medulla of the cat kidney. The purpose of these experiments was to observe whether this pattern is preserved or disrupted by a stimulus to renin release.
2. Plasma renin concentration in arterial samples and in the superficial and deep renal venous outflows was measured before and after haemorrhage which produced a 24 ± 6.7% drop in mean blood pressure in 13 cats.
3. After haemorrhage, total kidney plasma flow and glomerular filtration rate (GFR) did not change significantly. There was a rise in arterial plasma renin concentration. Venous minus arterial plasma renin concentration increased significantly in the deep venous outflow, but not in the superficial outflow.
4. The results suggest that both superficial and deep cortical venous drainage of the cat kidney should be considered when measuring renal renin release. In addition, they suggest that there may be differences in the response of superficial and deep juxtaglomerular apparatuses to haemorrhage.