Adenosine 3',5'-monophosphate in relation to inhibition of cervical smooth muscle activity in early pregnant women.

Contractile activity was registered in strips of cervical tissue obtained by needle biopsy from women in the first trimester of pregnancy. Dibutyryl cyclic adenosine-3',5'-monophosphate (5 x 10(-6) mol/l), isobutyryl methylxanthine (10(-4) mol/l), and forskolin (10(-5)-10(-4) mol/l), the latter two drugs known to increase the levels of endogenous cAMP, inhibited spontaneous muscle activity. The levels of tissue cAMP were determined in strips during relaxation induced by prostaglandin E2 or purified porcine relaxin and compared with cAMP levels in strips from the same women during contractile activity. Exposure to prostaglandin E2 but not to relaxin was followed by increased levels of cAMP. It is suggested that cAMP has a role as a second messenger in the prostaglandin E2-mediated relaxation of cervical smooth muscle.