Transfer of native insulin through the peritoneal membrane during CAPD in non-diabetic and diabetic patients

Because of its relatively small molecular size of 5800 daltons, insulin is a transperitoneally diffusable substance. Insulin is also known to be a mitogenic coadjuvant for mice fibroblasts, and safety of its long-term intraperitoneal use has been questioned because of the potential risk for peritoneal fibrosis. For similar reasons native insulin content of the peritoneal effluent should also not be neglected. To our knowledge, no sufficient data are available about native insulin transfer to dialysate during continuous ambulatory peritoneal dialysis (CAPD). In this study we measured plasma and dialysate immune-reactive insulin levels during a 4 hour peritoneal exchange in 9 nondiabetic and 4 type II diabetic end-stage renal disease patients on CAPD. In both plasma and dialysate, insulin levels were higher in diabetic patients. At hour 4 of dwell time, plasma insulin was 37.5 +/- 7.9 microU/mL in non-diabetics and 64.2 +/- 34.1 microU/mL in type II diabetics. In both groups, dialysate insulin was 1.5 to 2 x higher than their simultaneous peripheral vein insulin levels and was measured as 88.1 +/- 26.8 microU/mL in nondiabetic group and 101.7 +/- 52.6 microU/mL in the diabetic group at hour 4 (p < 0.005 vs 4 hour plasma level). In conclusion, in both diabetic and nondiabetic CAPD patients, native insulin was present in the dialysate in amounts exceeding simultaneous plasma levels. Equilibration with high portal vein insulin content through hepatic capsule may explain higher insulin concentrations measured in the dialysate.(ABSTRACT TRUNCATED AT 250 WORDS)