Identification of a Molecular Species in Porcine Ovarian Luteal Glutathione S-Transferase and Its Hormonal Regulation by Pituitary Gonadotropins

Glutathione S-transferase (GST) was purified to a homogenous state from the cytosol fraction of porcine corpora lutea. The present study showed that the final enzyme preparation consisted of a single molecular species of hepatic GSTA1-1, which has been identified from its enzymatic properties, amino acid composition, N-terminal amino acid sequences, and immunological reactivity. Furthermore, it is suggested that ovarian GST is involved in steroidogenesis, especially in the step of progesterone synthesis, from the following results. (1) The final enzyme preparation had a significant Δ5-3-ketosteroid isomerase activity, which acts in steroid synthesis. (2) GST activity in the cultured porcine granulosa cells was remarkably increased in the luteinizing process, which was induced by addition of pituitary gonadotropins such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH) to the culture system. (3) Changes of GST activity induced by FSH and LH were closely associated with progesterone production. (4) GST was detected within luteinizing and theca interna cells, but not in granulosa cells, by immunohistochemical staining of ovary tissues using anti-ovarian luteal-GST antibodies.