Changes in "active" and "inactive" renin in the juxtaglomerular apparatuses of rat nephrons and plasma induced by different salt intake.

The juxtaglomerular apparatuses (JGA) of deep and superficial nephrons were isolated by microbiopsy or by microdissection. Inactive renin content was determined by acidification of JGA or plasma to pH 3.0. In rats with low salt intake the renin content of superficial JGA was 13.4 +/- 3.0 ng AI/JGA/h before and 20.4 +/- 3.4 ng AI/JGA/h (n = 9), P less than 0.05) after acidification. The corresponding values for deep JGA were 9.1 +/- 1.2 ng AI/JGA/h and 12.7 +/- 2.7 ng AI/JGA/h (n = 9, P less than 0.01). The plasma renin concentration was 54.1 +/- 15.0 ng AI/ml/h before and 56.0 +/- 10.6 ng AI/JGA/h (n = 7, N.S.) after acidification. In rats with a normal salt intake the superficial renin JGA renin content was 11.6 +/- 2.3 ng AI/JGA/h before and 11.0 +/- 2.7 ng AI/JGA/h (n = 9, N.S.) after acidification. The renin content of deep JGA was 4.6 +/- 0.6 ng AI/JGA/h before and 8.6 +/- 3.1 ng AI/JGA/h (n = 9, P less than 0.005) after acidification. Plasma renin concentration was 34.5 +/- 4.7 ng AI/ml/h and did not change after acidification. In rats with a high salt intake superficial JGA content was 6.8 +/- 1.7 ng AI/JGA/h before and 8.4 +/- 2.1 ng AI/JGA/h (n = 9, N.S.) after acidification. The corresponding values for deep JGA were 5.7 +/- 1.6 ng AI/JGA/h and 6.9 +/- 1.6 ng AI/JGA/h (n = 9, N.S.) respectively. Plasma renin concentration was 13.1 +/- 1.1 ng AI/ml/h and this to 21.8 +/- 2.9 ng AI/ml/h (n = 8, P less than 0.01) after acidification. These results suggest that although the synthesis of active and inactive renin is linked, the secretion of the two forms may be independent.