The aim of the study was to evaluate the effect of verapamil (V) in patients with primary hypertension and ischaemic heart disease upon platelet membrane structure (by the use of an 4-maleimide-2, 2, 6, 6- tetramethylpiperidine-1-oxyl (MSL) spin label for electron paramagnetic resonance experiments) and ADP-, collagen- and ristocetin-induced platelet aggregation measured with an aggregometer. The examinations were performed in 23 patients before the administration of V and after 5 days of V therapy. In addition, in 10 patients the administration of V was preceded with the same examinations in vitro prior to and following a 30- minute incubation of platelet-rich plasma (PRP) with V and in parallel tests by adding CaCl2, to PRP previously incubated with V. In ex vivo studies, platelet aggregation examined with all the agonists was distinctly lower after the use of V; V induced also evident conformational changes in platelet membrane proteins. Similar changes were observed in in vitro studies. Moreover, the addition of CaCl2, 'improved' the platelet aggregation disturbed previously after the incubation with V and restored the conformational changes of the membrane proteins. It is supposed that platelet aggregation disturbances are due to structural changes in the membrane proteins observed upon administration of V.

Keywords: verapami, Hypertension, Platelet Aggregation, platelet membrane structure