Hormonal sensitivity of adenylate cyclase from human endometrium: modulation by estradiol

In human endometria, a membrane-bound adenylate cyclase is present, which is recovered in high yield in a low-speed particulate fraction. Neither the specific activity of the enzyme nor the response to modifiers that act through the regulatory subunit of the complex, are modified during the proliferative or secretory phase of the cycle. Surprisingly, we found that in vitro treatment of secretory endometrial membranes with 17 beta-estradiol stimulates 3- to 4-fold the activity of adenylate cyclase. However this response does not occur on proliferative membranes. The activation by estradiol is independent of the presence of guanylylimidodiphosphate and is additive to that of the nucleotide. Possibly, as the consequence of the phenomenon, the concentration of cyclic AMP is significantly higher in curretage samples obtained from patients during the secretory rather than in the proliferative phase of the cycle. To our knowledge this is the first evidence of a target-cell membrane-directed effect of sex steroids in humans.