Verapamil influences the effect of nonionic contrast agent on platelet membrane structure and aggregation.

Anticoagulant and antiplatelet function of NICM is weak, thereby presenting a hazard of coronary thrombus growth in patients subjected to coronary angiography. Similar antiplatelet effect was demonstrated for verapamil (V). The present study was designed to determine iopromide induced modifications in blood platelet membrane structure and aggregation in patients with primary hypertension and ischaemic heart disease receiving V compared to non-receivers of V. The blood for examinations was collected by Judkins' catheter placed in the vicinity of the coronary vessel ostium, and next centrifuged to obtain platelet-rich plasma. The ADP- and ristocetin (R)-induced blood platelet aggregation was determined by means of an aggregometer while their membrane structure was studied by electron paramagnetic resonance. The spin-label used, 4-maleimide-2, 2, 6, 6-tetramethyl-piperidine-1-oxyl (MSL) binds covalently to the -SH and -NH2 groups of platelet membrane proteins. The modifications in various spectral components, examined by means of a spectrometer, reflect conformational changes in these proteins. In non-receivers of V, iopromide diminished the aggregation, significantly in the case of ADP (p = 0.05), whereas in the receivers of V the iopromide-induced platelet aggregation examined with ADP did not change while with R was even enhanced (p = 0.05, Fig. 2). The platelet membrane protein conformation also changed due to iopromide: in non-receivers of V the accessibility of the above named groups for MSL was significantly reduced, p < 0.05, but in the receivers of V--inversely--significantly increased, p < 0.05. The results obtained confirm that in non-receivers of V, iopromide modifies the conformation of platelet membrane proteins which, in turn, may result in the lessening of the aggregation rate, favourable as regards the conditions of coronary thrombus growth. The tendency in the receivers of V was reverse and, however its nature remains obscure, this effect should be an indication for discontinuing the use of V several days before subjection the patient to coronary angiography.