Endogenous Sympathetic Activity in CAPD Patients: Its Relationship to Peritoneal Diffusion Capacity

Endogenous agents, as catecholamines, may influence peritoneal mass transport by modifying peritoneal blood flow. Such endogenous mechanisms could explain certain functional peculiarities of the peritoneum in CAPD patients. In 27 randomly selected patients on CAPD we calculated peritoneal mass-transfer coefficient (MTC) for urea, creatinine, uric acid and parathormone (PTH) using mathematical modelling techniques. Also we measured simultaneously the renin-angiotensin and catecholamine levels in blood and dialysate. The dialysate level of catecholamines and especially noradrenaline was significantly higher than the blood levels. Most of these patients had higher renin and aldosterone blood levels than the controls; we found no renin activity in the dialysate of any of these patients; (Plasma) aldosterone values correlated directly with renin activity. Multivariant analysis provided no evidence that the MTCs values were affected by two or more variables. Linear regression analysis of all variables studied showed direct correlation between dialysate noradrenaline and MTCs, and negative relationship between noradrenaline and ultrafiltration capacity. The catecholamine plasma levels, which were within the normal range, did not correlate with MTCs or with ultrafiltration. Our findings suggest that, in some cases, noradrenaline produced in the peritoneum may influence peritoneal mass transport through a vasoactive effect. Dialysate catecholamine levels correlate with that of plasma, but the latter does not influence peritoneal transport.