The Metabolism of Steroid Hormones in the Pituitary Gland of the Laying Hen

Abstract

[4-¹⁴C]-Labelled progesterone, androstenedione, testosterone, estrone and estradiol were incubated with the homogenates of pituitary gland from 150-day-old laying hens. The metabolic products were identified by their mobilities on the thin-layer chromatograms, and recrystallization to constant ³H: ¹⁴C ratio or constant specific activity. After incubation of [4-¹⁴C] progesterone with the pituitary gland tissue, it was converted to 5α-pregnane-3, 20-dione, 3α-hydroxy-5α-pregnan-20-one and 20α-hydroxypregn-4-en-3-one. [4-¹⁴C] Androstenedione was metabolized to testosterone and 5α-androstane-3, 17-dione. [4-¹⁴C] Testosterone was metabolized to androstenedione. [4-¹⁴C] Estrone was metabolized to estradiol. [4-¹⁴C] Estradiol was metabolized to estrone.
Twenty minutes after the intravenous injection of [³H] progesterone to the 150-dayold laying hens, 5α-pregnane-3, 20-dione, 3α-hydroxy-5α-pregnan-20-one and 20β-hydroxypregen-4-en-3-one were obtained as the metabolies from progesterone in the pituitary gland. Twenty minutes after the injection of [³H] estradiol to the hen, estrone was obtained as the metabolite from estradiol in the pituitary gland, and 40.2% of the radioactive steroid uptaked by the gland was recovered as estradiol in the tissue.
No conversion to 17α-hydroxyprogesterone from progesterone by the pituitary was observed both in in vitro and in vivo studies. Lacking in 17α-hydroxylase is characteristic of the target organs for steroid hormones such as pituitary, oviduct13), brain12) and epididymis16).