| Autor: |
van Meel, Jacques C A, Qian, Jiaqing, Timmermans, Pieter B M W M, van Zwieten, Pieter A |
| Zdroj: |
Journal of Pharmacy and Pharmacology; August 1983, Vol. 35 Issue: 8 p500-504, 5p |
| Abstrakt: |
The inhibitory effects of (+)- and (-)-verapamil on the hypertensive responses brought about by the α2-adrenoceptor agonist B-HT 920 were investigated in pithed normotensive rats. (-)-Verapamil was found to be about 4 times more potent with respect to depressing α2-pressor responses compared with (+)-verapamil. To rule out the effect of ‘unspecific’ vasodilatation after the administration of the stereoisomers of verapamil, vasopressin was continuously infused into the carotid artery of pithed rats in a separate series of experiments. In the course of this vasopressin infusion, new inhibitory activities of the stereoisomers of verapamil on α2–adrenoceptor-mediated pressor responses were determined. Under these circumstances, the potency ratio of (-)- vs (+)-verapamil was about 7. With the aid of a radioligand binding assay using [3H]clonidine to identify α2–adrenoceptors, low affinities were measured for the stereoisomers of verapamil. A Ki= 6170 nM for (-)-verapamil and a Ki= 41700 nM for (+)-verapamil were calculated. The results indicate that the interaction between α2-adrenoceptor-mediated pressor responses and calcium entry blockers, such as verapamil, is a stereoselective event. |
| Databáze: |
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