Lutropin regulation of steroidogenesis and specific protein synthesis in rat Leydig cells

In the testis steroidogenesis takes place in the Leydig cells (Hooker, 1970) and is under the control of lutropin, a glycoprotein hormone with a mol. wt. of about 30,000 consisting of 2 nonidentical subunits, which is secreted by the anterior pituitary (Hall, 1970). The main steroid secreted by the testis of the adult rat is testosterone (Eik-Nes, 1970). Cholesterol is the precursor for the synthesis of steroid hormones and its conversion into pregnenolone is stimulated by lutropin (Hall, 1970). The further conversion of pregnenolone into testosterone is not under the control of lutropin

Inhibition of Leydig Cell Steroidogenesis: Effect of Actinomycin D Before and After Preincubation of Leydig Cells In Vitro

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. Copyrigh