Immunolocalization of Inhibin/Activin Subunits and Steroidogenic Enzymes in Equine Neonatal Ovaries

Abstract

The objective of this study was to investigate the cellular immunolocalization of inhibin α and inhibin/activin (β_A and β_B) subunits and steroidogenic enzymes in neonatal equine ovaries. The ovaries were obtained from two equine neonates of 3 days and 18 days of age. The sections of ovarian tissues were immunostained by the avidin-biotin-peroxidase complex method (ABC) using polyclonal antisera raised against porcine inhibin α, inhibin/activin β_A and inhibin/activin β_B and bovine adrenal cholesterol side-chain cleavage cytochrome P450 (P450scc), human placental 3β-hydroxysteroid dehydrogenase (3βHSD), porcine testicular 17α-hydroxylase cytochrome P450 (P450c17), and human placental aromatase cytochrome P450 (P450arom). Inhibin α and inhibin/activin β_A subunits, but not inhibin/activin β_B subunits were expressed in the ovarian interstitial cells of equine neonates. P450scc and P450c17 were also identified in the ovarian interstitial cells and P450arom with weak immunostaining. However, 3βHSD was not found in the ovarian interstitial cells of the equine neonates. These results suggest that equine neonatal ovaries have the ability to synthesize inhibin A and steroid hormones, which may play some important physiological roles in the developing ovaries of equine neonates.