Skip to main content
ARS Home » Research » Publications at this Location » Publication #63591
Title: THE SUPPRESSIVE EFFECTS OF TESTOSTERONE ON GROWTH IN YOUNG CHICKENS APPEARSTO BE MEDICATED VIA A PERIPHERAL ANDROGEN RECEPTOR; STUDIES OF THE ANTIANDROGEN ICI 176,334.

Author
item FENNELL, M - RUTGERS UNIVERSITY
item RADECK, S - RUTGERS UNIVERSITY
item Proudman, John
item SCANES, C - RUTGERS UNIVERSITY

Submitted to: Journal Of Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Steroid hormones produced by the gonads are known to influence growth in both mammals and birds. These hormones, androgens in males and estrogens in females, act by binding to receptors located on the animal's cells. In mammals, it is known that androgens stimulate stimulate growth, especially muscle growth. In poultry, androgens will stimulate growth in turkeys but not in chickens. The same androgens which stimulate growth in the turkey cause an inhibition of growth in the chicken while still stimulating secendary sexual characteristics. This study was designed to determine the role of the androgen receptor in regulating these responses. The antiandrogen, ICI 176,334, has been shown in mammals to prevent binding of androgen to peripheral androgen receptors (those located outside the brain) while not affecting androgen receptors in the pituitary and brain that are thought to be responsible for sexual maturation. The results showed that the antiandrogen could completely suppress the comb growth that was induce by androgen treatment, demonstrating that peripheral androgen receptors were blocked. A low dose of antiandrogen partially overcame the suppressive effects of androgen on growth, but a high dose exhibited toxic effects. The results show that the growth suppressive effects of testosterone in chickens is mediated, at least in part, by the androgen receptor. These finding help in understanding how steroid hormones regulate growth, but further research is necessary to explain the difference between chickens and other meat-producing animals.

Technical Abstract: In chickens, androgens stimulate secondary sexual characteristics (e.g. comb) but inhibit growth and the immune tissues. The present study examined the effect of dietary ICI 176,334 (non-steroidal antiandrogen) on growth in chickens in the presence or absence of testosterone treatment (as silastic implants) from 2 to 6 weeks of age. Testosterone alone reduced body growth (average daily gain, shank - toe length, together with weights of the body, skeletal muscle and the bursa of Fabricus, an immune tissue), while stimulating comb development. At the low dose (5 mg/kg), ICI 176,334 alone had no effect on body growth or organ weight with the exception that comb weight was reduced. At the high dose (25 mg/kg), ICI 176,334 decreased growth (body weight, average daily gain, shank toe length), organ weights (breast muscle, bursa Fabricius, testis and comb weight). This may represent a toxic effect. As might be expected with an antiandrogen, ICI 176,334 (at either 5 or 25 mg/kg) completely suppressed the stimulation of comb growth evoked by testosterone. Similarly, ICI 176,334 (5 mg/kg) overcame, albeit partially, the growth suppressive effects of testosterone (on body weight, average daily gain, shank-toe length, breast muscle weight) and also inhibitory effects on the testis weight and bursa of Fabricius. The antiandrogen, ICI 176,334, did not influence the reduction in circulating concentrations of luteinizing hormone induced following testosterone treatment. The present data are consistent with the growth suppressive effects of testosterone in chickens being medicated via a peripheral androgen receptor. No effects of either testosterone or ICI 176,334 were observed on circulating concentrations of insulin-like growth factor-I despite the marked changes in growth rate.