[Secretion of the salivary glands of the medicinal leech Hirudo medicinalis inhibits ADP-induced aggregation of human platelets and platelet adhesion to a collagen-coated surface].

As was earlier demonstrated, secretion of medical leech exhibits high antithrombin activity of hirudin and inhibits contact activation of factor XII. Attempts were made to investigate the effects of the leech secretion on (i) the ADP-induced aggregation of platelets in suspension, registered by photometry according to Born, and (ii) platelet adhesion to the calf skin collagen-coated surface measured by scanning electron microscopy. The following results were obtained: 1) the secretion at doses of 0.13 vol % and 0.75 vol % inhibits the ADP-induced aggregation of gel-filtered human platelets by 50 and 97%, respectively; 2) the secretion inhibits the total adhesion and initial attachment of the gel-filtered platelets to the collagen substrate by 60-70% (dose 0.1-1.0 vol %) and 87-88% (dose 10 vol %); 3) platelet spreading on the collagen substrate and adhesion of the platelets from suspension to the upper surface of the spread platelets are inhibited by the secretion as well, but these effects are not statistically significant. The data obtained suggest that the secretion contains components which inhibit both the coagulating and platelet-vascular wall pathways of hemostasis.