Differential Alteration of the Reproductive Axis by Testosterone and Estrogen in Peripubertal and Adult Male Siberian Hamsters (Phodopus sungorus)

• Published in: Biology of reproduction Vol. 67; no. 3; pp. 706 - 711
• Main Authors: PAK, Toni R, LYNCH, G. Robert, TSAI, Pei-San
• Format: Journal Article
• Language: English
• Published: Madison, WI Society for the Study of Reproduction 01.09.2002
• Subjects: Aging; Animals; Biological and medical sciences; Cricetinae; Estradiol - administration & dosage; Estradiol - pharmacology; Follicle Stimulating Hormone - blood; Fundamental and applied biological sciences. Psychology; Leydig Cells - cytology; Leydig Cells - drug effects; Male; Phodopus; Reproduction - drug effects; Seminiferous Tubules - anatomy & histology; Seminiferous Tubules - drug effects; Sexual differentiation and maturation. Puberty. Climacterium; Sexual Maturation - drug effects; Spermatogenesis - drug effects; Testis - drug effects; Testis - growth & development; Testis - physiology; Testosterone - administration & dosage; Testosterone - pharmacology; Vertebrates: reproduction; Puberty; Androgen; Estrogen; Rodentia; 17β-Estradiol; Male; Ovarian hormone; Testosterone; Vertebrata; Reproduction; Mammalia; Testicular hormone; Phodopus sungorus; Sex steroid hormone; Hamster
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod.102.003434

In male Siberian hamsters, administration of adult physiological levels of testosterone (T) and estrogen (E 2 ) to juveniles inhibited pubertal onset by distinct pathways. It is presently unclear if T and E 2 also exert an inhibitory effect on the reproductive function of sexually mature and sexually maturing hamsters. This study aims to determine if there is an age-dependent decline in the sensitivity of the hypothalamic-pituitary-gonadal (HPG) axis to these inhibitory steroids and if their actions remain distinct. Peripubertal and adult male Siberian hamsters were implanted with a silastic capsule containing T, E 2 , or cholesterol (Ch, control). Testosterone treatment significantly reduced testes mass and length and impaired spermatogenesis in both ages. In contrast, E 2 treatment reduced testes mass only in peripubertal, but not adult, animals. In fact, E 2 treatment significantly increased testes mass in adults without altering spermatogenesis. In addition, circulating E 2 is very high immediately prior to pubertal onset and declines thereafter. Our results showed the inhibitory effects of T persist into adulthood whereas those of E 2 subside as the animals become sexually mature. The decreased sensitivity of the HPG axis to the inhibitory effects of E 2 in adult animals and the high level of circulating E 2 immediately prior to pubertal onset suggest E 2 may play an important role in the regulation of puberty in this species.