Heparin in clinical doses 'primes' granulocytes to subsequent activation as measured by myeloperoxidase release.

The author pre-incubated isolated human granulocytes with increasing doses of heparin (0-100 IU/mL) before subsequent stimulation with formyl-met-leu-phe. There was a dose-dependent increase in granulocyte activation as measured by myeloperoxidase release, quantitated in enzyme-immunoassay. This 'priming' effect of heparin was not due to activation of contaminating platelets or to endotoxin, and there was no reduction in granulocyte viability. Heparin-induced 'priming' of granulocytes may be clinically relevant in the setting of cardiopulmonary bypass. The author describes a sensitive and specific double antibody enzyme-immunoassay for myeloperoxidase from human granulocytes, with an inter-assay coefficient of variation of 12.6%, an intra-assay coefficient of variation of 4.3%, and a lower detection limit of 1.8 microg/l.