Relaxin-induced changes in adenosine 3',5'-monophosphate levels in the human cervix.

The effects of porcine relaxin on the levels of cAMP in human cervical tissue were studied in vitro. The specimens were obtained by needle biopsy from women undergoing hysterectomy, legal abortion in the first trimester or elective Caesarean section at term, and were incubated in Krebs-Ringer buffer for 15 min in the presence of porcine relaxin (5 micrograms/ml, 3000 GPU/mg). cAMP was determined using a modified protein binding assay. The concentration of cAMP was higher in pregnant than in non-pregnant women. Relaxin stimulated the production of cAMP in the 7th-8th week of gestation and at term but did not significantly alter the cervical cAMP levels in neither non-pregnant women nor in women in the 10th-12th week of pregnancy. Previous studies have shown that porcine relaxin reduces collagen synthesis in tissue from the human cervix and lower uterine segment. The present observations indicate that these effects can be mediated by cAMP.