Papaverine, cyclic AMP and the dependence of the rat aorta on extracellular calcium. |
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Authors: | F Demesy-Waeldele J C Stoclet |
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Affiliation: | Laboratoire de Pharmacodynamie, U.E.R. des Sciences pharmaceutiques, Université Louis Pasteur, 67083 Strasbourg, France |
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Abstract: | The spasmolytic effects of papaverine and dibutyryl cyclic AMP (db-cAMP) were compared on isometric contractile responses induced by addition of increasing amounts of external calcium to K+-depolarized or noradrenaline-stimulated rat aorta strips. Papaverine at a concentration active on depolarized strips (3 times 10(-5) moles/1) reduced the maximal contraction (Emax) elicited by Ca2+ in these preparations, while db-cAMP did not. Contrary to what was observed on depolarized aortae, the degree of inhibition of noradrenaline-stimulated strips did not decrease with increasing extracellular calcium concentration (Ca)e. Both db-cAMP and papaverine at a concentration which did not depress Emax (5 times 10(-6) moles/1) potentiated the relaxing effect of high (Ca)e on contractions elicited by noradrenaline. In conclusion, cyclic AMP is probably implicated in the mode of action of papaverine on the noradrenaline-stimulated rat aorta. At a concentration active on depolarized strips, papaverine is also able to impair contractility directly. |
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Keywords: | Vascular smooth muscle Papaverine Cyclic AMP Spasmolytic action Calcium dependece |
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