title: Effects of forskolin and isoproterenol on cyclic AMP and tension in the myometrium.
abstract: The effects of forskolin and isoproterenol on total cyclic AMP accumulation and relaxation were compared in uterine segments from estrogen-treated rabbits and term-pregnant rats. In the rabbit, forskolin (0.2-5.0 microM) inhibited spontaneous and acetylcholine-induced contractions and increased cyclic AMP levels. At lower doses forskolin significantly inhibited contractions but had little effect on cyclic AMP (cAMP) levels. Isoproterenol (0.005-0.5 microM), doses equi-effective to those of forskolin for inhibition of contractions, did not alter cyclic AMP levels. In the rat, forskolin (0.5 microM) and isoproterenol (0.05 microM) inhibited spontaneous and potassium-induced contractions by 80%. This reduction was accompanied by an increase in cyclic AMP levels, but the increase was significantly greater with forskolin than with isoproterenol. We conclude that: (1) cAMP may mediate relaxation under certain conditions but it is not an obligatory mediator, (2) some form of compartmentalization of cyclic AMP might exist in the myometrium.
mesh_terms: D000109:Acetylcholine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000818:Animals; D005576:Colforsin; D000242:Cyclic AMP / Q000032:analysis*; D004224:Diterpenes / Q000494:pharmacology*; D004347:Drug Interactions; D005260:Female; D007273:Injections, Intramuscular; D007545:Isoproterenol / Q000494:pharmacology*; D009215:Myometrium / Q000032:analysis / Q000187:drug effects*; D011247:Pregnancy; D011817:Rabbits; D051381:Rats; D014590:Uterine Contraction / Q000187:drug effects*
chemical_list: D004224:Diterpenes; D005576:Colforsin; D000242:Cyclic AMP; D007545:Isoproterenol; D000109:Acetylcholine