Adenylate Cyclase in the Corpus Luteum of the Rhesus Monkey, I. General Properties and Optimal Assay Conditions*

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Abstract
To characterize the adenylate cyclase system of the primate corpus luteum, the conversion of [.alpha.-32P] ATP to [32P]cAMP was assayed in preparations of luteal tissue obtained from rhesus monkeys on days 17-19 of the menstrual cycle. Basal, gonadotropin (hCG [human chorionic gonadotropin]; 250 nM)-sensitive, and guanine nucleotide ([GMP-P(NH)P]; 10 .mu.M) sensitive cAMP production were influenced by the pH, osomolality, and ionic strength of the assay buffer. As the concentration of Mg2+ increased from 2 to 10 mM, adenylate cyclase activity was enhanced; however, the relative stimulation by hCG plus GMP-P(NH)P was maximal when the Mg2+ concentration approximated that of ATP plus EDTA. In contrast, the presence of Ca2+ inhibitied basal, hCG-stimulated, and GMP-P(NH)P-stimulated cAMP production. Adenylate cyclase activity was substate dependent at ATP concentration from 0.7-4.5 mM; however, higher concentrations of ATP did not alter cAMP production. The relative stimulation by hCG and GMP-P(NH)P was independent of ATP levels when the ATP of Mg ratio was constant. The rate of cAMP production was constant during 30 min of incubation at 37.degree. C, with the ATP concentration maintained at > 87% of initial levels. Adenylate cyclase activity was 10-fold greater in luteal tissue from the superovulated rat than in that from the cycling rhesus monkeys; however, relative stimulation by hCG and GMP-P(NH)P was qualitatively similar in the 2 species. The existence of an adenylate cyclase system was demonstrated in the corpus luteum of the rhesus monkey during the menstrual cycle. Some general properties and optimal assay conditions for the gonadotropin-sensitive adenylate cyclase are established.

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