MaRGA Meeting, 2004: Abstracts

19: Physiology and Immunology

Androgens and Aging in Male Marmosets

J.A. French, K.J. Patera, S. Boykins and A.M. Puffer

Affiliation: Callitrichid Research Center, University of Nebraska at Omaha,
Omaha, NE

Aging is associated with dramatic changes in gonadal steroid production in men and women, including increases in hormones in the early stages of life (e.g., peripubertally) and decreases in hormone titers in later years. Similar patterns are apparent in a wide range of mammals, suggesting a ubiquitous underlying process. Callitrichid primates may represent an exception to this rule, at least for females. In tamarins, while females do experience a reduction in ovulatory incidence as they age, ovarian luteal tissue does not appear to lose its steroidogenic properties in older females (Tardif & Ziegler, Biol. Reprod., 1992). We explored patterns of changes in steroid hormone production in male marmosets whether male marmosets exhibit changes in androgens as they age. We measured concentrations of urinary testosterone (uT), urinary estradiol (uE), and urinary cortisol (uC) in male marmosets (Callithrix kuhlii) via enzyme immunoassays. Concentrations of uT were high in infants less than three months of age, and levels were lowest in males 5-6 months of age. AT 12 months of age (the age of earliest documented conceptive mating in males), mean levels of uT exceeded 1,000 ng/mg Cr, suggesting this value as a diagnostic for reproductive maturation. Levels of uT and uC were not different in sons residing in family groups and while paired with females, but were elevated in males housed in same-sex groups. In contrast, uE became elevated in males after pairing with adult females. Across the lifespan, uT levels were characterized by a weak inverted U-shaped function, with peak levels at 6-8 years of age and delining levels thereafter. There was a weak but significant correlation between age and uT from 6-15 years of age (r = 0.25, p < 0.01). The results of GnRH challenges revealed that gonadal tissue not only retained its steroidogenic properties in older male marmosets, but may be more sensitive to GnRH challenge than in younger males. Change in plasma T and E concentrations were highly and positively correlated with age (r's = 0.85 and 0.86, p < 0.01, respectively). These results suggest that alterations in hypothalamic-pituitary-gonadal activity associated with age in male marmosets are similar to those of other mammals, but unlike other primates (and like female callitrichids), steroidogenic cells in the gonads appear to retain function well into adult aging. The results point to the utility of the male marmoset as a model for the effects of aging on androgen-mediated traits.

Supported by NSF (00-91030) and NIH (HD 42882).