PROTEIN KINASE ACTIVITY OF PURIFIED LEYDIG CELLS: LOW PROTEIN KINASE ACTIVITY CAUSES IMPAIRED STEROIDOGENESIS BY BAND TWO CELLS.

Using a 0–32% continuous metrizamide density gradient, interstitial cells could be separated into five distinct bands. Cells localized in bands 1 (B₁), 2 (B₂), and 3 (B₃) were isolated and incubated for lh with or without human chorionic gonadotropin (hCG). Both B₂ and B₃ cells responded to hCG with increased cyclic AMP formation, but only B₃ cells produced significantly more testosterone. Protein kinase activity of B₂ cells was found to be extremely low compared with B₁ and B₃ cells. Additional treatment of B₃ cells with collagenase did not cause any change in protein kinase activity. These results indicate that decreased protein kinase activity may be responsible for impaired testosterone synthesis in B₂ cells.