Influence of long-term isolation on the production and metabolism of gonadal sex steroids in male and female rats.

The influence of long-term isolation on in vitro testosterone metabolism in the gonad, and on plasma testosterone and estradiol-17β concentrations, was studied in male and female Wistar rats. The following metabolites of testosterone-4-¹⁴C were isolated: androstenedione, 11β-hydroxyandrostenedione, androstenediol, estradiol-17β, estrone, and estriol. Biosynthesis of androstenedione and estriol was not influenced by isolation; biosynthesis of 11β-hydroxyandrostenedione and androstenediol was increased after isolation in females, while biosynthesis of estradiol-17β and estrone was lowered in this sex. Plasma testosterone showed a significant increase in isolated males, while estradiol-17β was unaffected by isolation. The general effect produced by isolation seems to result in an increase of androgens in both sexes. In females such effect is evident in a higher conversion of testosterone into androgens and in a lower biosynthesis of estrogens. In males the increase of androgens is evident in the higher level of plasma testosterone. Some behavioral effects of long term isolation were established by means of two aggression tests, which showed an increase of aggressiveness. These findings suggest that the condition of housing may be a major parameter affecting the production of sex steroids.