Acute cAMP Stimulation in Leydig Cells: Rapid Accumulation of a Protein Similar to That Detected in Adrenal Cortex and Corpus Luteum

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Abstract
Addition of cAMP (as the dibutyryl compound) to a primary culture of mouse Leydig cells caused the accumulation of a protein, i(b), with the same dependence on cAMP concentration as the increase in testosterone synthesis. Stimulation of both protein i(b) and testosterone production were inhibited by cycloheximide. Additionally, cAMP caused repression of synthesis of another protein, p(b), with the same approximate molecular weight (28,000 daltons) as i(b), but more basic isoelectric point. This behavior resembles an event which has been documented in the adrenal cortex (Krueger, R.J., and Orme-Johnson, N.R., J. Biol. Chem., 258, 10159-10167, 1983) and corpus luteum (Pon, L.A., and Orme-Johnson, N.R., J. Biol. Chem., 261, 6594-6599, 1986). The discovery of these proteins in a third steroid-producing cell type and the close correlation between conditions causing increased steroid synthesis and increased i(b) production is further indication that protein i(b) may be an intermediary in peptide hormone or cAMP control of steroid hormone biosynthesis.