Importance of glycosylation for hepatic clearance of renal renin.

Abstract

Three differently glycosylated forms of renin (renin A, B-1, and B-2) were highly purified from rat kidneys by pepstatin-aminohexyl-Sepharose affinity chromatography and by serial lectin affinity chromatography on concanavalin A (con A) and lentil lectin-Sepharose, and the role of glycosylation of renin was investigated. Renin A and renin B-1 were loosely and tightly bound to con A, respectively, but did not bind to lentil lectin. Renin B-2 bound to both con A and lentil lectin. These three forms of renin were all similar in their physicochemical characteristics, including molecular weight, isoelectric point, specific activity, Km, optimum pH, and antigenicity. Each form of renin, labeled with 125I and given intravenously to anesthetized rats, disappeared from the circulation at different rates (metabolic clearance rates of 5.05 +/- 1.02, 17.1 +/- 2.5, and 36.0 +/- 4.1 ml.min-1.kg-1 for renins A, B-1, and B-2, respectively). Labeled renin A distributed to a similar extent in the liver and kidney (21.2 +/- 0.2 and 15.2 +/- 0.8% of the injected dose, respectively), whereas renins B-1 and B-2 were distributed predominantly in the liver (56.3 +/- 1.2 and 72.3 +/- 3.7% of the injected dose, respectively) and to a lesser extent in the kidney (4.3 +/- 0.3 and 2.1 +/- 0.2%, respectively). Deglycosylation of renin B-1 with endoglycosidase F resulted in no loss of its enzymatic activity or antigenicity but greatly reduced the metabolic clearance rate to 18% (from 17.1 +/- 2.5 to 3.09 +/- 0.17 ml.min-1.kg-1). Deglycosylation of renin B-1 greatly decreased its uptake by the liver (from 56.3 +/- 1.2 to 3.3 +/- 0.2%) and increased its uptake by the kidney (from 4.3 +/- 0.3 to 23.9 +/- 0.9%). These studies indicate the importance of glycosylation of renin for its hepatic uptake and metabolic clearance rate.