Formation and Activation of Renin in Vivo

Active and acid activated renin was measured in glomeruli of rats obtained by microbiopsy and in rat plasma. Sodium depletion increased total and active renin in the juxtaglomerular apparatus and approximately one third of the renin was in an inactive form in sodium depletion. Sodium loading decreased active and total renin and there was no inactive renin present. In plasma changes in a similar direction occurred for active and total renin but in sodium depletion there was no inactive renin present while with sodium loading approximately 40% was in the inactive form. Haemorrhage caused a release of active renin in both sodium states and did not alter the renin content of the J.G.A. Increased delivery of sodium chloride to the macula densa increased the active renin content of J.G.A. but did not alter the total renin content. These results are compatible with two different roles of the renin angiotensin system. One being concerned with intrarenal regulation of glomerular filtration and renal blood flow and the other with maintenance of vascular tone. The conversion of inactive renin to active renin being of particular importance in the regulation of G.F.R.