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

The effects of chronic uraemia and serial acetate (HDA) or bicarbonate (HDB) haemodialysis on the aggregation, thromboxane B2 (TXB2) release and cyclic AMP (cAMP) concentration of platelets from arterial blood were studied in 14 uraemic patients (6 dialysed and 8 conservatively treated) and 10 controls. Platelets from uraemic patients, either dialysed or treated conservatively, exhibited a significantly higher cAMP level (P less than 0.005), a lower TXB2 level (P less than 0.01), and a lower aggregability (P less than 0.001) than the controls. The platelet cAMP level was more markedly decreased after HDB than after HDA (P less than 0.05). Greater increases in platelet aggregation (P less than 0.05) and TXB2 formation were observed after HDB than after HDA. The concentration of platelet cAMP and aggregability, and also the platelet cAMP and the TXB2 level showed a significantly negative correlation (r = -0.7, P less than 0.05 and r = -0.60, P less than 0.05, respectively). There was a positive correlation between the platelet-derived TXB2 and the aggregability (r = 0.67, P less than 0.05). Although most patients had secondary hyperparathyroidism, the serum parathyroid hormone level did not correlate closely with the cAMP, TXB2 or aggregation results. The dysfunction of uraemic platelets accompanied by a reduced TXB2 release may be explained by an increased cAMP and a decreased arachidonic acid availability. HDB improves the platelet function to a greater degree than does HDA.