The effect of preincubating purified Leydig cells in Eagle's medium and the subsequent effect of the mRNA synthesis inhibitor actinomycin D on LH‐stimulated testosterone synthesis has been investigated. The inhibitory effect obtained was found to decrease with the period of preincubation; with 0, 1, 2 and 3 h preincubation before the addition of LH (100 ng/ml) 36.5 ± 3.9, 31.2 ± 2.5, 17.8 ± 3.8 and 13.6 ± 2.9% inhibition occurred respectively when actinomycin D (6.4 μM) was added and the cells were incubated for 2 h (means ± SEM, n = 5). During the first hour of incubation with LH and actinomycin D no inhibition occurred in cells that had been preincubated for 3 h. These results suggest that during preincubation and independently of LH, synthesis of intermediates (possibly mRNA(s)) required for stimulation of steroidogenesis may take place and that subsequent stimulation of steroidogenesis by LH occurs without further de novo mRNA synthesis. Copyright

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International Journal of Andrology

Cooke, B.A., Janszen, F., & van Driel, M. (1978). Inhibition of Leydig Cell Steroidogenesis: Effect of Actinomycin D Before and After Preincubation of Leydig Cells In Vitro. International Journal of Andrology, 1, 240–246. doi:10.1111/j.1365-2605.1978.tb00019.x