title: Mechanism of relaxant action of papaverine. VI. Sodium ion dependence of its effect on 45Ca-efflux in guinea-pig taenia coli.
abstract: The present study was undertaken to investigate the roles of sodium ion and the cyclic AMP system in the relaxant effect of papaverine. The effects of papaverine on the 45Ca-efflux and the mechanical activity of guinea-pig taenia coli were tested in solutions in which the concentration of sodium ion was varied and compared with those of dibutyryl cyclic AMP. Papaverine dose-dependently caused an acceleration of 45Ca-efflux and the synchronous relaxation of a depolarized preparation in normal bathing solution. Dibutyryl cyclic AMP mimicked these effects of papaverine. In Na-free solution, papaverine lost its ability to accelerate the 45Ca-efflux, and its relaxant activity was markedly reduced, while dibutyryl cyclic AMP had neither an effect on the 45Ca-efflux nor an effect on the muscle relaxation in Na-free solution. Reintroduction of a small amount of sodium ion to the solution, however, recovered these effects of papaverine and dibutyryl cyclic AMP on the 45Ca-efflux and the muscle relaxation. These findings indicate that the relaxant effect of papaverine may be in part due to an increase in cyclic AMP-mediated Ca-efflux which requires the presence of external sodium ion. The sodium ion dependence of this Ca-efflux process was also discussed.
authors.forename: N
authors.initials: N
authors.lastname: Sunagane
authors.forename: T
authors.initials: T
authors.lastname: Ogawa
authors.forename: T
authors.initials: T
authors.lastname: Uruno
authors.forename: K
authors.initials: K
authors.lastname: Kubota
mesh_terms: D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects*; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D010208:Papaverine / Q000494:pharmacology*; D012964:Sodium / Q000494:pharmacology*
chemical_list: D003994:Bucladesine; D012964:Sodium; D010208:Papaverine; D002118:Calcium