Plasma concentrations of 18-hydroxycorticosterone and aldosterone in continuous ambulatory peritoneal dialysis and hemodialysis patients

This study explores the hypothesis that the continuous ultrafiltration that accompanies continuous ambulatory peritoneal dialysis (CAPD) produces greater activation of the renin-angiotensin aldosterone axis than does the intermittent ultrafiltration that accompanies thrice weekly hemodialysis (HD). Plasma renin activity (PRA), active renin (AR), total renin (TR), inactive renin (IR), 18-hydroxycorticosterone (18-OH-B), aldosterone (PAC), and cortisol were measured in plasma from CAPD (n = 6) and HD (n = 10) patients. Blood from CAPD patients was sampled at 8 AM after overnight recumbency and at 12 noon after four hours ambulation. Blood from HD patients was sampled immediately pre-HD (8 AM) and post-HD (12 noon) at both 8 AM and 12 noon. PRA (P less than 0.01), AR (P less than 0.01), and AR/TR (100%; P less than 0.01) were higher in CAPD than in HD. IR and TR were not different in the two groups. Plasma 18-OH-B was normal in HD but markedly elevated in CAPD. 18-OH-B was higher in CAPD than in HD at 8 AM (P less than 0.05) and at 12 noon (P less than 0.05). Plasma cortisol was not different in the two groups. We conclude that the greater degree of renin activation in CAPD versus HD contributes to the higher levels of 18-OH-B and PAC observed in CAPD patients.