Abstract
The present study was carried out to determine the molecular weight of renin and to investigate the presence of an acid-activatable form of renin (inactive renin) in the plasma and kidney of rats after dietary sodium restriction. The cytosol fraction and renin granule fraction were prepared from the kidney cortex homogenate. Renin activity and the molecular weight of renin were measured by radioimmunoassay and by gel filtration, respectively. The intake of sodium-deficient diet for 4 weeks resulted in a 5-fold increase in plasma renin activity and led to a 2-fold increase in the renin activities of cytosol fraction and renin granule fraction. However, no significant change was observed in the protein content of the cytosol or renin granule fraction. The molecular weights of renin in the plasma, cytosol fraction and renin granule fraction from sodium-restricted rats were all 40000, being similar to those of control rats. In addition, no change in molecular weight or in activity was seen after acidification. These results indicate that active renin of regular size (M. W. 40000) is synthesized in the juxtaglomerular cells, stored in granules, and secreted into circulating blood following chronic sodium restriction.
