Effects of androgens on dietary self-selection and carcass composition in male rats

The aromatizable androgen testosterone propionate (TP; .2 mg/day) increased protein and carbohydrate intake and stimulated body weight gain in gonadectomized (Gdx) male rats. A higher dose of TP (2.0 mg/day) increased protein, but not carbohydrate, intake and was less effective in stimulating body weight gain than the lower dose of TP. Postmortem carcass analyses revealed that the elevated protein intake of both TP-tested groups was associated with increased carcass protein content. The decreased weight of rats treated with the high dose of TP was due to a reduction in body fat content. The nonaromatizable androgen 5 alpha-dihydrotestosterone propionate (DHTP; .2 or 2.0 mg/day) also increased protein (but not carbohydrate) intake and body weight gain in Gdx male rats, but it did not alter carcass composition. Unlike TP, the two doses of DHTP were equally effective, but neither dose of DHTP was as effective as the low dose of TP in stimulating protein and carbohydrate intake and body weight gain. The results of these experiments suggest that (a) androgens can increase selection of dietary protein whether or not they exert significant protein anabolic effects, (b) the 5 alpha-reduced product of testosterone, 5 alpha-dihydrotestosterone, is not the major metabolite responsible for the increases in protein and caloric intake and in body weight caused by TP, and (c) the decreases in carbohydrate intake and adiposity in rats treated with the high dose of TP may be mediated by aromatized (estrogenic) metabolites of the androgen.