RESUMO
The pathogenesis of depressed platelet activity in uremia is still unknown. The influence of some uremic toxins on platelet aggregation (PLA) and prostaglandin metabolism in 50 uremic patients treated by hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD) was studied. Fifty-seven healthy volunteers (HVs) served for reference values. Adenosine diphosphate (ADP) and thrombin (Thr) were used as agonists of PLA. PLA was determined using the Born method. Malonyldialdehyde (MDA) levels in platelets as an indicator of prostaglandin metabolism, after stimulation with arachidonic acid, were measured according to Stuart. The relationship of PLA and prostaglandin metabolism with plasma concentrations of methylguanidine (MG), guanidinosuccinic acid (GSA), and creatinine (Cr) was assessed. PLA-ADP values in regular HD patients (42 +/- 5 mm) were significantly lower than in CAPD patients (65 +/- 8 mm) and HVs (73 +/- 3 mm). PLA-Thr values in HD patients (25 +/- 4 mm) were significantly lower than in CAPD patients (34.9 mm) and HVs (36 +/- 3 mm). MDA levels in HD patients (7 +/- 1 nmol/L/10(9)) were significantly lower than in CAPD patients (12 +/- 2 nmol/L/10(9)) and HVs (15 +/- 1 nmol/L/10(9)). In HD patients, inverse correlations of PLA-ADP with MG levels (r = -0.92), PLA-Thr with Cr levels (r = -89), and MDA levels with GSA levels (r = -0.86) were found. In CAPD patients, no relationship of PLA and MDA with uremic toxins was observed. Depressed activity of platelets and prostaglandin metabolism was strongly expressed in HD patients.
