[Ultrastructural study on the effect of an inhibitor of platelet aggregation (author's transl)].

10-Methoxy-1,6-dimethyl-ergoline-8 beta-methanol-(5-bromonicotinate) (nicergoline, Sermion) is introduced into human platelet-rich plasma at different stages of collagen-, ADP- or epinephrine-induced aggregation. Ultrastructural fixation is processed while aggregation on the same plasma sample is recorded. If introduced before the aggregating agent, nicergoline completely neutralises its action and the platelets become spherical. The microtubule marginal bundle is disorganized and both open and dense canalicular systems are modified. If intoduced after the aggregating agent, nicergoline immediately stops the aggregation and disaggregation follows, with complete separation of the platelets. Morphology of microtubules and canalicular systems depend on the time before application of nicergoline. Nicergoline stops the induction of aggregation as well as ADP release. Disaggregation is an active process involving the microtubules.