STEROID HORMONES AND THE DEVELOPMENT OF THE REPRODUCTIVE SYSTEM IN THE PULLET1

Abstract

White Leghorn pullets received testosterone propionate (TP) and estradiol dipropionate (ED) alone and in combination from the 20th to the 39th day post-hatching. The 5.0 [mu]g and 25.0 [mu]g daily dosages of the androgen increased comb weights 100% and 700%, respectively, but when injected simultaneously with the estrogen the effectiveness of the TP was decreased about 25%. TP had no significant effect on oviduct weight when given separately at any of the 3 dosages whereas 25.0 [mu]g daily of ED increased oviduct weight 600%. When the highest dosages of the two sexogens were given together, oviduct growth was augmented; an increase of about 1400% occurred. Ovarian and pituitary weights were not affected by hormone treatments and pituitary gonadotropin content was essentially normal except in the series which received 25.0 [mu]g daily of the two sexogens. The amount of gonadotropin was markedly decreased in this series. Administration of progesterone, anhydroxyprogesterone, pregnenolone, dehydroisoandrosterone, and Reichstein''s Substance S acetate at dosage levels of 5.0 [mu]g and 25.0 [mu]g daily, alone and in combination with 25.0 [mu]g of ED did not produce an augmentation of oviduct growth. Furthermore, these steroids had greater inhibitory effects than did the TP treatments. Comb and ovarian weights were slightly lower than normal and the pituitary content of gonadotropin was markedly decreased. Progesterone was given at dosages of 100 [mu]g, 250 [mu]g, and 500 [mu]g daily and the 500 [mu]g also was injected with 25.0 [mu]g of ED. Progesterone had only slight effects on comb, ovary, and pituitary weights or pituitary potency when given alone. When progesterone was injected in combination with ED, however, comb and ovarian growth were markedly inhibited and pituitary secretion of gonadotropin was almost completely suppressed. Oviduct growth was greatly stimulated in this series and was about 4200% greater than in the control. An androgen comparable to testosterone may be present in the female bird at sexual maturity and this hormone acting in concert with an estrogen may be necessary for the normal development of the avian reproductive system. The 5 other steroids tested, including progesterone, appear to play no major role in the maturation of the reproductive system of the female bird.