EFFECT OF STRESS ON THE PROFILE OF PLASMA STEROIDS IN BABOONS (PAPIO HAMADRYAS)

Abstract

Adult baboons (5 males and 5 females) were exposed to immobilization stress by being strapped to a table in a horizontal position for 2 h. In females the experiment was performed during both the follicular and luteal phase. Peripheral blood was withdrawn at frequent intervals, the 1st sample just before immobilization and the last 3 days later. A number of steroids were measured in blood plasma samples by radioimmunoassay (17-hydroxypregnenolone, 17-hydroxyprogesterone, pregnenolone, testosterone, dihydrotestosterone, progesterone, 20.alpha.-dihydroprogesterone, estrone, estradiol) or competitive protein binding (cortisol) techniques. The cortisol levels exhibited a marked increase in both sexes. This increase was observed already during the immobilization and lasted for approximately 24 h. A similar, even more pronounced increase was seen in 17-hydroxypregnenolone, 17-hydroxyprogesterone and pregnenolone levels. A marked, long-lasting (72 h) decrease of testosterone and dihydrotestosterone levels was a consistent finding in male baboons. This was not observed in the females which exhibited a marked decrease (duration 48 h) of progesterone and 20.alpha.-dihydroprogesterone levels during the luteal phase and a significant decrease (duration > 24 h) of estradiol and estrone concentrations during the follicular phase. Stress has a marked inhibitory action on gonadal function both in male and female baboons. In females the inhibition of steroidogenetic function is exerted both on the ovarian follicles and on the corpus luteum.