Adenylyl Cyclase Messenger Ribonucleic Acid in Myometrium: Splice Variant of Type IV

Regulation of uterine tone during pregnancy and parturition involves G protein-coupled receptors that modulate cellular levels of cAMP. Cyclic AMP is synthesized by a family of at least nine adenylyl cyclase enzymes that have unique tissue distributions, basal activities, and modes of regulation. Little is known regarding the expression of adenylyl cyclase isoforms in myometrium. Reverse transcriptionpolymerase chain reaction (PCR) was performed using RNA extracted from freshly dissected rat uteri and a cell line of homogenous rat myometrial cells. Using PCR primers specific for adenylyl cyclases I-IX, mRNA encoding adenylyl cyclases II-IX were identified in both fresh and cultured myometrial cells. A splice variant of adenylyl cyclase type IV was also identified in RNA from both sources. These data show that multiple isoforms of adenylyl cyclases are expressed at the mRNA level in myometrial cells and suggest that the regulation of cellular levels of cAMP likely involves a complex integration of cellular second messengers acting upon multiple isoforms of adenylyl cyclases.