Gonadal luteinizing hormone receptors and adenylate cyclase: transfer of functional ovarian luteinizing hormone receptors to adrenal fasciculata cells.

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RESUMO

Luteinized rat ovaries contain a high concentration of particulate luteinizing hormone (lutropin, LH) receptors and a small quantity of lipid-associated receptors that float in the 360,000 X g supernatant fraction of ovarian homogenates. During fractionation of Lubrol-solubilized LH receptors and adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] from the ovary and testis, LH receptors and adenylate cyclase were coincident on gel filtration, but could be resolved during ion-exchange chromatography of soluble ovarian preparations and were completely separated by lectin-affinity chromatography on Sepharose-concanavalin A. For further analysis of receptor-adenylate cyclase coupling, the lipid-rich fraction of ovarian luteal cells was used to transfer gonadal LH receptors to isolated adrenal fasciculata cells. The lipid vesicles obtained from ovarian homogenates by flotation at 360,000 X g contained 5--10% of the ovarian LH receptors and were devoid of adenylate cyclase activity. During incubation of lipid-associated receptors with dispersed rat fasciculata cells at 16 degrees C, progressive incorporation of LH binding sites into the adrenal cells was observed. When adrenal cells bearing heterotopic LH receptors were incubated with 1 nM human choriogonadotropin, cyclic AMP production was consistently stimulated, with an accompanying increase in corticosterone production. These results indicate that LH receptors exist as separate entities from adenylate cyclase in the gonadal cell membrane and can become functionally coupled to adenylate cyclase to evoke cyclic AMP production and steroidogenesis in the host adrenal cells to which they are transferred.

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