[The regulation of renin synthesis]

Secretion and synthesis of renin are stimulated by the lack of angiotensin II and by a low sodium intake. They are inhibited by a high sodium intake, by denervation and by propranolol. A high sodium intake can overcome the effect of the lack of angiotensin II. A low sodium balance and the lack of angiotensin II did not have additive effects. The sodium effects did not appear to depend on the presence of the macula densa, the presence of angiotensin II, or the presence of the nerve supply. It was not evaluated whether baroreceptors may be important in allowing sodium effects to be processed, but in the experiments conducted there were no significant changes in blood pressure associated with alterations in sodium balance. Sodium balance has an important effect on synthesis and secretion. This effect does not appear to be mediated by the usual set of controls and raises questions as to the signal relating sodium balance to renin synthesis. Secretion does appear to depend on macula densa. The role of the macula densa appears to control the basal level of renin secretion and to permit the conversion and processing of prorenin to renin.