[Catabolism of brain natriuretic peptide (BNP) in normal and nephrotic rat kidney]

The major metabolic change that characterizes nephrotic syndrome (NS) is hypoalbuminemia. Edema, which is a well-recognized clinical feature, often results in disorder of peripheral circulation and congestive heart failure. We previously reported that the albumin content of kidney lysosomal proteins was increased more than ten-fold in nephrotic rats compared to control rats, suggesting that kidney lysosomes play an important role in protein degradation in NS. The present study was carried out to elucidate the role of catabolism of BNP, which is one of the functional protein-natriuretic peptides. We injected puromysin aminonucleoside(PAN) to induce the nephrotic rat state and isolated kidney lysosomes from normal and nephrotic rat kidney cortex by our methods. Immunoblot analysis of tricine-SDS polyacrylamide gel electrophoresis of rat kidney lysosomal proteins revealed the presence of an immuno-reactive peptide band, corresponding to the endogenous BNP. In addition, this was reduced as compared with the normal control. These result suggest that kidney lysosomes play an important role in BNP metabolism to maintain body fluid homeostasis and regulate blood pressure levels.