Regulation of C6 glioma cell steroidogenesis by adenosine 3',5'-cyclic monophosphate.

Incubation of C6 glioma cells in the presence of aminoglutethimide, an inhibitor of cholesterol metabolism, together with either adenosine 3',5'-cyclic monophosphate (cAMP) analogues or agents that increase cAMP synthesis, such as cholera toxin, forskolin, and isoproterenol, stimulated the rate of pregnenolone formation by their isolated mitochondria. This effect of cAMP was blocked by the antagonist (Rp)-cAMPS. The incorporation rate of mevalonolactone into pregnenolone was also increased by the stimulation of adenylyl cyclase activity in intact C6 cells. It is concluded that cAMP stimulates glial cell steroidogenesis by increasing the movement of the substrate, cholesterol, to the mitochondria, where it will be metabolized to pregnenolone by the side chain cleavage cytochrome P450 enzyme.