Intraperitoneal atrial natriuretic peptide increases peritoneal fluid and solute removal

Abstract

Background. Atrial natriuretic peptide (ANP) is a hormone with well-known diuretic and vasodilating properties. Recently it was reported that ANP could increase the peritoneal fluid formation and increase peritoneal solute clearance. This study investigated the effect of ANP on peritoneal fluid and solute transport characteristics. Methods. Eighteen male Sprague-Dawley rats were divided into three groups. A four-hour dwell study using 25 mL 2.27% glucose dialysis solution with 50 μg/kg ANP (N = 6, H-ANP) or 5 μg/kg ANP (N = 6, L-ANP) or without ANP (N = 8, control) and frequent dialysate and blood sampling was done in each rat. Radiolabeled human albumin (RISA) was added to the solution as an intraperitoneal volume marker. Results. The intraperitoneal volume was significantly higher in the H-ANP group as compared with the control group and the L-ANP group. The drainage volume was 26.2 ± 1.1, 25.5 ± 0.7, and 29.8 ± 0.8 mL for the control, L-ANP, and H-ANP groups, respectively (P < 0.01). This was related to significant differences in the peritoneal fluid absorption rates (KE; estimated as the RISA elimination coefficient): 39 ± 3, 38 ± 3, and 19 ± 4 μL/min, and in the direct lymphatic absorption rate (KEB; estimated as the clearance of RISA from dialysate to blood): 7 ± 1, 6 ± 1, and 4 ± 1 μL/min for the control, L-ANP, and H-ANP groups, respectively (all P < 0.01). No differences were found in the intraperitoneal volume, KE, and KEB between the control group and the L-ANP group. The diffusive mass transport coefficient (KBD) for urea, sodium, potassium, and total protein did not differ among the three groups. However, the glucose D/D0 was significantly higher, and the KBD for glucose was significantly lower in the H-ANP group as compared with the other two groups. Solute clearances (+175% for sodium and +26% for potassium) were significantly increased in the H-ANP group, mainly as a result of the increased fluid removal in this group.