Impairment of adenylate cyclase activity and G-proteins in human uterine leiomyoma

The mechanisms responsible for the growth of uterine leiomyoma (a frequent cause of infertility in women) are largely unknown. Some data supports that cAMP plays a role in the growth of uterine cells but there are no reports on the status of the cAMP producing system in this human benign neoplasia. In this study, biopsies from leiomyoma and the adjacent myometrium were tak en from menstruating women subjected to total hysterectomy for leiomyoma, A denylate cyclase activity was determined by a protein-binding method, and t he expression of alpha (s), alpha (i1/2), alpha (i3) and alpha (i0)) G-prot ein subunits was analysed by immunoblot. The leiomyoma samples exhibited a decreased expression of a(s) and a(i1/2) with respect to the adjacent myome trial tissue. No differences were observed in alpha (i3) and alpha (i0) pro tein expression. The basal adenylate cyclase activity as well as the effica cy las assessed by the maximal stimulation levels) of either forskolin or, to a lesser extent, Gpp[NH]p on stimulation the enzyme activity was signifi cantly lower in leiomyoma than in myometrium, whereas the potency (as asses sed by the ED50 values) of these two agents did not vary. Present data indi cate that the human leiomyoma is associated with low levels of cAMP. It is conceivable that the loss of sensitivity of adenylate cyclase to endogenous regulatory molecules could be related to the pathogenesis of human leiomyo mas given that cAMP inhibits the MAP-kinase cascade in uterine tissues. (C) 2000 Harcourt Publishers Ltd.