The effects of bicarbonate and acetate haemodialysis on platelet cyclic AMP concentration, thromboxane B2 release and aggregation

The roles of platelet function, thromboxane, blood lipids and nitric oxide in hypertension of children and adolescents

The roles of platelet function, plasma lipids and nitric oxide (NO) were studied in adolescent patients with essential hypertension (JEHT group), with chronic renal failure (CRF) associated with hypertension (CRFH group), and CRF patients with normal blood pressure (CRF group), as compared with normal controls (cont. group). Platelet aggregation and the thromboxane B(2)(TxB(2)) level were significantly higher in the JEHT and CRFH groups as compared with the cont. group, whereas they were significantly lower in the CRF group. On the other hand, the platelet cAMP level was significantly lower in the JEHT and CRFH groups than in the cont. group. The plasma NO level was significantly higher only in the JEHT as compared with the cont. group (120 +/- 39 and 89 +/- 21 microM, respectively). The plasma total cholesterol, triglyceride and LDL cholesterol concentrations were normal in the JEHT group, but high in the CRF and CRFH group, the HDL cholesterol level was lower in the CRF and CRFH groups as compared with the cont. and JEHT groups. There was a positive correlation between the platelet aggregation and the TxB(2)level and between the BP and the platelet aggregation. In conclusion, hyperlipidaemia is commonly present in uraemia with haemodialysis, but is not specific for hypertension in children, while an increased platelet function is frequently associated with hypertension. The increased NO level might play a compensatory role in JEHT.

The effect of erythropoietin on platelet function in uraemic children on haemodialysis

The effect of 1-year erythropoietin (rHu-EPO) treatment on the bleeding time, platelet aggregation, ATP and thromboxane B2 (TXB2) release, cyclic AMP (cAMP) concentration and platelet surface positive charge were studied in 8 haemodialysed children with chronic uraemia and 8 controls. The pre-dialysis haematocrit (Hct) was 0.21 + 0.01 before and 0.36 + 0.01 following 1 year of rHu-EPO therapy. At the end of this period the pre-dialysis bleeding time became normal (P < 0.05); this was associated with a significant increase in platelet aggregability (P < 0.05), ATP release (P < 0.05) and TXB2 production (P < 0.01), and with a significant decrease in platelet cAMP concentration (P < 0.01). A further increase in platelet aggregation, ATP release and TXB2 production and a decrease in platelet cAMP concentration was observed following bicarbonate haemodialysis (BHD) (P < 0.01). There was a significant positive correlation between platelet aggregation and ATP release (r = 0.78, P < 0.05), as well as platelet aggregation and TXB2 production (r = 0.68, P < 0.05). A significant negative correlation was found between platelet aggregability and cAMP concentration (r = -0.7, P < 0.05). The platelet surface positive charge, which was significantly lower in the patients than in the controls (P < 0.01), did not change during rHu-EPO therapy, nevertheless BHD resulted in a significant increase (P < 0.05), suggesting the surface charge may influence platelet aggregation. In an in vitro and an in vivo study, rHu-EPO and the higher Hct did not increase platelet aggregation directly. Long-term administration of rHu-EPO stimulated complex functional and biochemical changes in the platelets of uraemic patients, which resulted in an improved aggregability.

Laser aggregometer studies, ATP release and thromboxane B2 release and cAMP concentration of the platelets in nephrotic syndrome

Platelet function was studied in 56 children with nephrotic syndrome, 33 were on oral prednisolone (P) treatment (group 1), while 23 were in early (< 6 months) remission (group 2): 12 on P (group 2a) and 11 not on P (group 2b), and there were 18 controls (group 3). The following tests were used: platelet aggregation with collagen in a laser rheoaggregometer; adenosine triphosphate (ATP) release: during aggregation with luciferin-luciferase in a lumiaggregometer; thromboxane B2 (TXB2) release: by radioimmunoassay; platelet cAMP concentration: by binding assay. The changes in plasma cholesterol (C) and triglycerides (TG) were compared with the platelet aggregation results. Patients in group 1 and 2 exhibited significantly higher aggregability, TXB2 release and ATP release in response to collagen than those in group 3 (p < 0.01), but there was no difference between groups 1 and 2 or groups 2a and 2b. Some differences were observed between the histological groups. Patients with IgA and SLE nephropathy displayed higher aggregability than those with minimal change nephrotic syndrome in remission (p < 0.05). The highest level was in membranous nephropathy. The platelet cyclic adenosine monophosphate (cAMP) concentration was significantly lower in groups 1 and 2 than in group 3 (p < 0.001). No differences were observed between groups 1 and 2 or between groups 2a and 2b. Plasma C and TG levels did not show any correlation with the platelet aggregation.(ABSTRACT TRUNCATED AT 250 WORDS)