Inhibin/activin subunit mRNA expression in human granulosa-luteal cells

Abstract

We studied the expression of inhibin/activin subunit mRNAs in granulosa-luteal cells of preovulatory ovarian follicles obtained from women undergoing in vitro fertilization, and in corpus luteum tissue samples of early pregnancy. Northern analysis of granulosa-luteal cell and corpus luteum RNA with single-stranded cDNA or cRNA probes revealed an 1.6-kb mRNA for the α subunit and about 6.0-, 4.0-, 2.8-, and 1.7-kb transcripts for the β A subunit. No clear hybridization signal for the β B subunit could be detected. The relative expression levels of α and β A subunit mRNAs were determined at 2-day intervals in granulosa-luteal cells cultured for 5 to 11 days. The levels of α subunit mRNAs declined steadily with increasing culture age, whereas those of β A remained unchanged. Reverse transcription-polymerase chain reaction analysis with 35 amplification cycles confirmed the expression of α and β A subunit mRNAs in cultured granulosa-luteal cells. The β B transcripts were also weakly detectable by this sensitive assay. In situ hybridization of human early pregnancy corpus luteum revealed intense hybridization with the α cRNA probe and a weaker signal for the β A subunit in the granulosa cell compartment. We conclude that: (1) the inhibin α and β A subunits (and to a lesser extent β B) are expressed in cultured human granulosa-luteal cells; (2) during extended culture periods the α/β A mRNA expression ratio decreases; and that (3) the α and β A subunit mRNA expression is observed in the granulosa cell compartment of early pregnancy corpora lutea.