REGULATION OF INHIBIN ALPHA-SUBUNIT AND BETA-B-SUBUNIT MESSENGER-RNA LEVELS IN RAT SERTOLI CELLS

The hormonal regulation of the expression of the inhibin α-subunit and βB-subunit genes was studied in cultured rat Sertoli cells. The a-subunit mRNA level increased during incubation of the cells in the presence of follicle-stimulating hormone (FSH), reaching maximal levels within 1.5 h. This stimulation was mimicked by addition of dibutyryl-cyclic AMP, indicating that FSH action on the α-subunit gene is exerted via cyclic AMP. Inhibition of translation by cycloheximide (CX) caused upregulation of the α-subunit mRNA, and did not block the effect of FSH on the level of this mRNA. In FSH-stimulated cells, the half-life of the a-subunit mRNA was 6 h, and this half-life was prolonged by inhibition of transcription using actinomycin D (AD). It is concluded that the effect of FSH on a-subunit mRNA expression represents a direct effect on the a-subunit gene, and that a-subunit mRNA levels are influenced by a short-lived mRNA destabilizing protein. The levels of two βB-subumi mRNAs (4.2 kb and 3.5 kb) were not affected by FSH or dbcAMP. However, these mRNAs were also upregulated by CX treatment. Experiments using AD showed that the 4.2 kb mRNA is less stable than the 3.5 kb mRNA. The differential regulation of the inhibin α- and βB-subunit mRNAs is discussed. © 1990.