Effect of amino acid based dialysate on peritoneal blood flow and permeability in stable CAPD patients: a potential role for nitric oxide?

Amino acid dialysis solution 1.1% (Nutrineal) contains L-arginine, a substrate for nitric oxide (NO) synthesis. NO causes vasodilation in many organs. To investigate effects of the amino acid dialysis solution on peritoneal permeability and perfusion, standard peritoneal permeability analyses were performed in 10 stable CAPD patients; one with Nutrineal and another with glucose dialysate (Dianeal 1.36%). The mass transfer area coefficient (MTAC) of nitrate and cGMP were calculated to study a possible role of NO. The MTAC of CO2 was measured to estimate peritoneal blood flow. The MTAC of CO2 was higher during the 4-hour dwell with the amino acid solution: median 93 ml/min (amino acid solution) vs. 60 ml/min (glucose solution); p < 0.01. This suggests an increased peritoneal blood flow during the administration of amino acids. Also the MTACs of low molecular weight solutes were greater with amino acids compared to glucose: creatinine 11.6 ml/min vs. 10.0, urea 19.0 vs. 16.6, urate 9.5 vs. 8.0; p < or = 0.01 for all. This points to an increased effective peritoneal surface area during amino acids. The clearances of the macromolecules beta 2-microglobulin and alpha 2-macroglobulin were also greater with the amino acid dialysis solution (p < 0.05), but there was only a small increase in the clearances of albumin and IgG. The increase in albumin loss during the 4-hour dwell with amino acids was only marginal. The MTACs of nitrate and cGMP were similar with the 2 solutions, without evidence of local production of these solutes. No difference was found between the 2 solutions in the dialysate concentrations of the prostaglandins PGE2, 6-keto-PGF1 alpha, PGF2 alpha and TxB2. The transcapillary ultrafiltration rate was higher during the amino acid dwell (p < 0.01), but no significant difference in net ultrafiltration was found, because the lymphatic absorption tended to be slightly greater with amino acids. The difference in transcapillary ultrafiltration with the 2 solutions was probably blood flow dependent, as the peritoneal filtration fraction was essentially the same in the 2 experiments. It is concluded that amino acid dialysis solution had a vasoactive effect. It mainly influenced the peritoneal blood flow and the effective peritoneal surface area. These effects could not be attributed to NO, as judged from nitrate or cGMP MTACs.