Katsumi Wakabayashi

The effect of synthetic estrogen upon the biosynthesis in vitro of androgen and luteinizing hormone in the rat

Abstract Two-month-old male rats of the Wistar strain were treated with hexestrol (estrogen) for 4 weeks (2.5 mg each once a week) to examine the effect of synthetic estrogen on the biosynthesis of androgen in testes and of luteinizing hormone in anterior pituitary glands. Testicular homogenate and microsomal fractions obtained from these rats were incubated with radioactive precursors such as [4-14C]pregnenolone, 4-14C]progesterone, 17α-hydroxy-4-14C iprogesterone and [4-14C]androstenedione. The activities of enzymes related to androgen formation, apart from that of 17α-pregnene-C-17-C-20 lyase, were strongly reduced by hexestrol treatment. Testosterone formation from progesterone in testicular homogenate was severely inhibited by the hexestrol treatment and progesterone added as substrate was catabolized mainly to 3α-hydroxy-5α-pregnan-20-one, which had no androgenic activity. However, testosterone formation from progesterone incubated with intact testicular homogenate in hexestrol-containing medium remained at the level of a control lacking hexestrol in the incubation medium. On the basis of these results, the direct action of hexestrol upon testicular enzymes related to steroid biotransformation is discussed. Anterior pituitary lobes of hexestrol-treated and intact rats were incubated with [14C]leucine, and the luteinizing hormone fractions were separated by immuno-chemical methods. The incorporation of [14C]leucine into the luteinizing hormone fraction was measured. The biosynthetic activity of luteinizing hormone was significantly lowered per unit weight of the tissue, but the total activity per gland was nog significantly influenced by hexestrol treatment.