Effects of vasodilators on peritoneal solute and fluid transport in rat peritoneal dialysis

The pharmacological manipulation by vasodilators of peritoneal solutes and fluid kinetics was investigated. Rats were dialyzed for 240 minutes with 30 mL 4.25% glucose dialysate containing dextran 70. An angiotensin-converting enzyme inhibitor (captopril), three calcium channel blockers (nicardipine, diltiazem, and verapamil), and an +/-blocker (maxisylite) were administered intraperitoneally at various concentrations. Membrane permeability to urea, glucose, and protein, actual net ultrafiltration rate (UFR), transcapillary ultrafiltration rate (TCUFR), and peritoneal net fluid absorption rate (PNFAR) were measured. All three vasodilators caused a decrease in blood pressure, which, except for moxisylite, was associated with a decrease in net UFR. Captopril and the three calcium antagonists increased PNFAR dose dependently. Captopril increased membrane permeability to small and large molecular solutes, with a consequent decrease in TCUFR. Nicardipine and verapamil increased permeability to urea and glucose but not to protein. Only the latter decreased TCUFR. Diltiazem caused no change in permeability. In conclusion, various vasodilators administered intraperitoneally affect peritoneal solute and fluid transport differently. This should, perhaps, be taken into consideration when working with continuous ambulatory peritoneal dialysis (CAPD) patients to whom antihypertensive drugs are administered in large doses.