Inactive renin in peritoneal fluid--an independent system or a transport form of circulating renin?

Active and inactive renin have been studied in peritoneal fluid and plasma of six patients with ascites and four patients on peritoneal dialysis (using concentrated dialysate). Acid-pepsin and trypsin activation gave similar results. In ascitic patients mean (+/- s.e.) plasma active renin was very high (0.31 +/- 0.99 pmol angiotensin l/l/s) compared with normal subjects (0.31 +/- 0.08 pmol ANG l/l/s). Plasma inactive renin (1.27 +/- 0.30 pmol ANG l/l/s) was similar to normal subjects (1.31 +/- 0.31 pmol ANG l/l/s) while the mean percentage of total renin which was inactive was 29.7 and 76.5. In ascitic fluid, active renin was very low (0.36 +/- 0.09 pmol ANG l/l/s) but inactive renin (2.15 +/- 0.28 pmol ANG l/l/s) was higher than plasma. Percentage of total renin inactive was 85.8. Peritoneal dialysate showed even smaller amounts of active renin but similar inactive renin with 95.4 per cent inactive (versus 73.8 in their plasma). Peritoneal fluid inactive renin was similar to that in plasma by affigel chromatography and gel filtration and showed, after activation, similar pH optima and Michaelis constants to plasma and peritoneal active renin.