Stage Dependent Expression of Inhibin α and β-B Subunits during the Cycle of the Rat Seminiferous Epithelium*

Abstract

In order to elucidate the putative role of inhibin in regulation of spermatogenesis, expression of inhibin subunits was examined at defined stages of the cycle of the rat seminiferous epithelium. Twenty 2-mm segments of seminiferous tubules at stages XIII-I, II-VI, VII-VIII, and IX-XII were dissected using the transillumination technique and subunit specific messenger RNAs (mRNAs) were quantitated by filter hybridization. The alpha and beta-B subunit mRNAs varied significantly in different stages, the highest levels of both alpha and beta-B subunit expression were seen in stages XIII-I and the lowest in stages VII-VIII. The hybridization signals obtained with beta-actin probe were not significantly different between different stages indicating that the differences in the quantities of subunit mRNAs in different stages were not due to different amounts of RNA blotted. beta-A subunit mRNA levels were below the detection limit of the filter hybridization method. These data demonstrate that expression of inhibin alpha and beta-B subunits in the rat testis is stage dependent and suggest a paracrine role for inhibin-related peptides in regulation of spermatogenesis.

Regulated production of activin A and inhibin B throughout the cycle of the seminiferous epithelium in the rat

“…Production of the inhibin B subunits (a and b B ) and the inhibin B protein is primarily under the control of circulating FSH, but also displays a cyclical pattern of production, with the highest levels of subunit mRNA at stages XIII-IV and lowest at stages VI-VIII (Bhasin et al 1989, Kaipia et al 1991, Buzzard et al 2004. Measurement of inhibin protein using a RIA directed against the a-subunit of inhibin confirmed that immunoreactive inhibin production mirrors the mRNA expression data with highest levels in tubule fragments from stages XIII-VI and the lowest content and secretion at stages VII-VIII, under both basal and FSH-stimulated conditions (Gonzales et al 1989, Klaij et al 1994.…”

Involvement of p21WAF1/Cip1, CDK4 and Rb in activin A mediated signaling leading to hepatoma cell growth inhibition

“…Further downstream events in the signaling cascade of activin A in mammalian cells are largely unknown. Activin A induces changes in calcium concentration (Mine et al, 1989) and activation of a pertussis toxin-sensitive G protein (Kaipia et al, 1993;Bhasin et al, 1989) in hepatocytes. It was further found, using the yeast twohybrid system, that the p21 ras farnesyltransferase (FNTA) a subunit, is bound to the TGFb and activin type I receptors, and is phosphorylated and released intracellularly upon ligand binding (Wang et al, 1996).…”

Seasonal Changes in Spermatogenesis and Immunolocalization of Inhibin/Activin Subunits in the Wild Male Ground Squirrel (<i>Citellus dauricus Brandt</i>)

“…The various inhibin/activin subunits have been localized in testes as messenger RNA and proteins. The expression of mRNA in Sertoli cells varies with the stage of the seminiferous cycle [6], with differences between the various subunits possibly reflecting differential production of activin and inhibin [7]. Some seasonal male breeders, such as stallions [5,8,9], rams [10] and Japanese monkeys [11][12][13], show seasonal changes in circulating inhibin concentrations in accordance with testicular activity.…”