Renin uptake by the right kidney in the rat following partial clamping of the left renal artery.

Renin secretion from both kidneys was studied in eleven Wistar rats for 40 min after partial clamping of the left renal artery. 14C Inulin and 3H para aminohippuric acid clearance and the arterial and venous plasma renin concentrations were measured in each kidney during control and experimental procedures. After clamping, the arterial plasma renin concentration increased and correlated positively with the plasma renin concentration in both renal veins. However, the plasma renin concentration of the right renal vein was lower than the arterial concentration (P < 0.01). The slope correlating the two variables is significantly lower than unity (P < 0.05, n = 19). As the left kidney secreted a large amount of renin, calculation of secretion by the right kidney decreased to negative values, implying renin uptake by this kidney. These data suggest the existence of a balance between the two kidneys. Renin secretion appears to maintain an equilibrium between release by the juxtaglomerular apparatus and removal from the blood into interstitial space. Release seems to predominate in the hypoperfused kidney, and removal in the contralateral kidney. This may result from the increase of the circulating angiotensin II, since we observed a direct correlation between renin uptake and the arterial plasma renin concentration.