Heparin inhibits FMLP and Con-A dependent activation of human polymorphonuclear leucocytes in vitro.

The effects in vitro of heparin on different functions of human neutrophilic leucocytes were assessed. Granulocyte aggregation, enzyme release and superoxide anion generation induced by FMLP (10(-6) M), ConA (30 micrograms/ml), and A 23187 (5 microM) were evaluated. Heparin was able to inhibit, in a dose-dependent way, FMLP-mediated and ConA-mediated granulocyte activation. Heparin inhibited cellular aggregation at the final concentration of 100-500 micrograms/ml, while the inhibiting effect on enzyme release and superoxide anion production was present at lower concentrations (10-100 micrograms/ml). No activity was observed on A 23187-induced granulocyte stimulation. The inhibiting effect of heparin on FMLP-induced granulocyte activation proved to be time-dependent. The hypothesis that an interaction of heparin with cells may possibly initiate the inhibitory effect is proposed.