Evidence that luteinizing hormone-stimulated differentiation of purified ovarian thecal-interstitial cells is mediated by both type I and type II adenosine 3',5'-monophosphate-dependent protein kinases.

LH has been shown to be the principal hormone regulating ovarian thecal-interstitial cell (TIC) differentiation. It has been well documented that LH stimulates cAMP production and that cAMP analogs mimick the stimulatory actions of LH, but the mechanisms by which LH and cAMP stimulate TIC differentiation are unknown. The purpose of these studies was to characterize LH-stimulated differentiation of isolated TIC in serum-free medium and examine the role of cAMP-dependent protein kinase (PKA) isoenzymes in TIC differentiation. Highly purified (greater than 90%) TIC which were free from granulosa cell contamination were isolated from collagenase-dispersed ovaries of hypophysectomized immature rats by Percoll gradient centrifugation. When the purified TIC (20,000 viable cells/well) were cultured (2 days) in serum-free medium (0.2 ml in 96-well plates), low levels of steroids were produced. LH stimulated a dose-related (ED50 = 2.6 +/- 0.4 ng/ml) increase (50-fold) in androsterone, the principal androgen produced. LH stimulated an immediate dose-related increase in cAMP production, but there was a 20-h lag before LH stimulated an increase in androsterone production, which reached maximum levels at 30 h. LH-stimulated progesterone production increased immediately to a maximum at 10 h, then progesterone levels decreased as androsterone production increased. To determine the role of PKA in stimulating androsterone and progesterone production, TIC were cultured (2 days) with 8-aminohexylamino-cAMP (100 microM) plus N6-benzoyl-cAMP (30 microM) or 8-thiomethyl-cAMP (30 microM) plus N6-benzoyl-cAMP (30 microM) to directly and selectively activate type I or type II PKA, respectively. Selective activation of either isoenzyme increased androsterone and progesterone production by TIC. Immunoblots revealed that either type I or type II PKA increased the contents of P450scc and P45017 alpha in TIC. This is the first demonstration that direct activation of either type I or type II PKA stimulates TIC differentiation. These results indicate that LH stimulates TIC differentiation by a mechanism mediated by activation of one or both PKA isoenzymes.