Immunocytochemical localization of adenylyl cyclase in human myometrium

The enzyme adenylyl cyclase (AC) plays a pivotal role in smooth muscle relaxation. Biochemical evidence suggests that AC is predominantly located in the outer layers of the myometrium; however, neither immunocytochemical nor histochemical studies have been undertaken to demonstrate the specific cellular distribution of the enzyme in this tissue. As part of an ongoing study of the human myometrium, a polyclonal antibody against types V and VI AC was used to detect the presence of these isoforms in sections of formalin-fixed, wax-embedded myometrial tissue. A positive reaction was seen in the cytoplasm of the smooth muscle cells with the midmyometrial area having the greatest number of positive cells, when compared to the subserosal and subendometrial areas. It is hypothesized that AC isoform type VI is the predominant isoform present in the myometrium and that the percentage distribution of positive cells reflects the area of highest myometrial activity during parturition.