Transmural pressure inhibits prorenin processing in juxtaglomerular cell

Pressure control of renin secretion involves a complex integration of shear stress, stretch, and transmural pressure (TP). This study was designed to delineate TP control of renin secretion with minimal influence of shear stress or stretch and to determine its mechanism. Rat juxtaglomerular (JG) cells were applied to a TP-loading apparatus for 12 h. In cells conditioned with atmospheric pressure or atmospheric pressure + 40 mmHg, renin secretion rate (RSR) averaged 29.6 ± 3.7 and 14.5 ± 3.3% (P < 0.05, n = 8 cultures), respectively, and active renin content (ARC) averaged 47.3 ± 4.6 and 38.4 ± 3.4 ng of ANG I · h^-1 · million cells^-1 (P < 0.05, n = 10 cultures), respectively. Total renin content and renin mRNA levels were unaffected by TP. The TP-induced decrease in RSR was prevented by Ca²⁺-free medium and the Ca²⁺ channel blocker verapamil and was attenuated by thapsigargin and caffeine, which deplete intracellular Ca²⁺ stores. Thapsigargin and caffeine, but not Ca²⁺-free medium or verapamil, prevented TP-induced decreases in ARC. The adenylate cyclase activator forskolin did not modulate TP-induced decreases in RSR or ARC. These findings suggest that TP not only stimulates Ca²⁺ influx but also inhibits prorenin processing through an intracellular Ca²⁺ store-dependent mechanism and thus inhibits active renin secretion by JG cells.