Effects of rat urinary arginine esterases on rat kidney to release renin

Urinary kallikrein has been reported to activate human plasma inactive renin. Our previous report suggests that rat urinary kallikrein releases active renin from rat renal cortical slices. Recently, McPartland et al. were able to separate the A esterase activity of male rat urine into two components: A1 and A2. To evaluate whether these other urine arginine esterases release renin from the kidney, esterases A1 and A2 were isolated from male rat urine using DEAE-Sephadex chromatography and superfused to rat renal cortical slices. The renin-stimulating action of these enzymes was compared to that of rat urinary kallikrein. Rat urinary kallikrein stimulated renin release in a dose-dependent fashion between 70--140 milliesterase units (mEU)/ml. Esterase A2 dose stimulated renin release significantly between 120--140 mEU/ml. However, esterase A1 did not stimulate renin release at concentrations between 70--140 mEU/ml. Although Trasylol completely abolished kallikrein and esterase A2 stimulated renin release, soybean trypsin inhibitor blocked only esterase A2-stimulated renin release. The physiological role and site of origin of the A1 and A2 esterases is unknown. However, similar to kallikrein, esterase A2 is a potent stimulator of renin release and may be physiologically important for the release and activation of renin in the kidney.