Testosterone, progesterone, and corticosterone titers were measured by RIA in plasma of stressed and control pregnant rats and their male and female fetuses on days 17, 18, 19, and 21 of gestation and on the day of birth. The regimen of stress used (three 45-min periods of restraint under intense illumination daily from days 14-21 of pregnancy) causes failure of masculinization and defeminization of behavioral potentials in male offspring. In fetuses of both sexes, corticosterone titers increased sharply between days 17 and 18 postconception (pc) to a peak that was maintained through day 19 and then declined. This pattern resembled that obtained for testosterone in control male fetuses in which the levels of testosterone also rose sharply between days 17 and 18 pc. Corticosterone titers were elevated in samples obtained during the middle of the stress session from both the mothers (serum) and their male and female fetuses (plasma). Increased corticosterone levels were no longer evident in samples obtained from fetuses 75-165 min after the end of a stress session. Testosterone titers were altered by stress only in male fetuses. Their testosterone levels were elevated on day 17 pc, and the surge on days 18 and 19 pc, characteristic of control males, was absent in samples obtained 75-165 min after termination of stress. Progesterone titers were not affected by stress in either mothers or their fetuses. In both stressed and control groups, progesterone concentrations were identical in male and female fetuses, were higher in mothers than in fetuses, and declined in both fetuses and mothers between days 19 and 21 pc. Thus, a persistent effect of stress was observed only on testosterone and only in males.
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