Renal renin responses to changes in volume status and perfusion pressure.

The effects on juxtaglomerular apparatus (JGA) renin activity of maneuvers known to acutely alter renin secretory rates were studied in rats. Five groups of rats were studied: group I: control; group II: 1% volume expansion; group III: 10% volume expansion; group IV: hypotensive hemorrhage; and group V: aortic clamping. Superficial (S) JGA renin activity was decreased in group II and further decreased in group III. Deep (D) JGA renin activity did not change. After hypotensive hemorrhage both S- and D-JGA renin activity increased. Similar results were seen after aortic clamping, although the increase in D-JGA renin activity was significantly less. These results indicate that S- and D-JGA renin activity may be under the control of different stimuli and may vary independently. They also support the concept that acute changes in renin secretion may be related to changes in renin synthesis.