CHANGES IN THE EXPRESSION OF ADENYLYL CYCLASES IN THE RAT UTERUS DURING THE COURSE OF PREGNANCY

The changes in the expression of the various adenylyl cyclases (ACs) i n the rat uterus during the course of pregnancy and after delivery wer e examined by Northern blot analysis and AC assay. Northern blot analy sis revealed that five isoforms of ACs (AC2, AC4, AC6, AC7, and AC9) w ere expressed in the rat uterus, AC6 being the most abundant. The leve l of expression of these ACs increased 1.7- to 3.4-fold during the cou rse of pregnancy and diminished near term and after delivery. The high est level of expression in each type of AC was consistently seen on Da y 17 of pregnancy, and the relative increase of expression, as compare d to that in nonpregnant rats, was as follows: AC2 > AC4 > AC7 > AC9 > AC6. In agreement with these findings, both basal and forskolin-stimu lated AC activities exhibited a 2- to 3-fold increase during the cours e of pregnancy, followed by a decrease near term. Our data indicate th at post-receptor events, namely marked changes in the level of AC mRNA (and presumably proteins) occur during pregnancy and after delivery a nd that they contribute to the essential role of cAMP in maintaining u terus quiescence.