[Catecholamine-sensitive adenylate cyclase activity and beta-adrenoreceptors of the myometrium in various functional...

Adenylate cyclase of the rabbit myometrium possesses different sensitivity to catecholamines in different functional states: in state of functional rest and labour the enzyme is activated by isoproterenol, in the state of pregnancy this activation is absent almost completely. The investigated functional states of myometrium are characterized by different density of beta-adrenoreceptors: density of beta-adrenoreceptors in the state of functional rest is 134 +/- 14 fmol/mg of protein, pregnancy -74 +/- 12 fmol/mg of protein, labour -80 +/- 11 fmol/mg. Dissociation constants of [3H]dihydroalprenolol for beta-adrenoreceptors of myometrium in states of functional rest, pregnancy and labour are 7.5 +/- 0.5 nM, 6.2 +/- 0.5 nM, 4.8 +/- 0.1 nM, respectively.