Properties of detergent-solubilized adenylate cyclase and gonadotropin receptors of testis and ovary.

The relationship between solubilized hormone-binding sites and adenylate cyclase was examined in detergent extracts of particulate testis and ovarian fractions. Both basal and fluoride-stimulated activities of the particulate enzyme were markedly increased in the presence of detergents, and about 60% of the enzyme activity was recovered as the soluble form in the 300,000 g supernatant. Enhancement of adenylate cyclase activity was more marked with Lubrol PX and WX than with Triton X-100, and the highest recovery and activation of adenylate cyclase were obtained with 0.5% Lubrol PX. The particulate and solubilized testicular enzymes were more active in the presence of Mn2+, and the detergent-extracted soluble ovarian cyclase showed a small and inconstant response to gonadotropin. Fractionation of Lubrol-solubilized testis and ovarian preparations on Sepharose 6B showed two peaks of free gonadotropin receptors. The binding activity eluted with Kav of 0.32 corresponded to the receptor sites previously characterized in detergent-solubilized gonadal particles, and was coincident with the elution profile of adenylate cyclase activity. An additional peak of binding activity with Kav of 0.56 was not accompanied by detectable adenylate cyclase activity. These observations suggest that the peak of larger molecular size could represent dissociated receptors or binding sites which were not coupled to adenylate cyclase.