Endocrinology, Vol 116, 640-645, Copyright © 1985 by Endocrine Society

ARTICLES

Gonadal status influences developmental patterns of serum prolactin in female rhesus monkeys housed outdoors

ME Wilson, ML Walker, SM Schwartz and TP Gordon

Although estradiol (E2) is thought to facilitate PRL secretion under certain conditions in female primates, the role of E2 or other ovarian products in the control of PRL secretion during puberty is unknown. The present study examined the influence of gonadal status on serum PRL levels in prepubertal monkeys housed in an outdoor environment. Basal levels of PRL were examined in three groups of spring-born females that were studied from 12 to 28 months of age (May 1982 to September 1983): gonadally intact (INT; n = 8), ovariectomized (OVX; n = 5), and ovariectomized and treated chronically with E2 (E2OVX; n = 5). All groups exhibited a significant annual rhythm in PRL levels with peaks (10-20 ng/ml) at 14 and 26 months (June to July) and a nadir (less than 2 ng/ml) at 19 months (November to December). Basal PRL levels were significantly higher from 12 to 15 months (May to August) in E2OVX subjects, with OVX having significantly greater concentrations than INT females. Group differences were not evident during the period of minimal secretion from 16 to 20 months (September to January). Finally, levels were again significantly higher in both E2OVX and OVX subjects during the subsequent period from 21 to 27 months (February to August). Although serum levels of E2 were lower in INT (30.9 +/- 2.3 pg/ml) than E2OVX females (51.4 +/- 4.0 pg/ml), group differences in PRL could not be attributed to E2 since OVX females, with no measurable levels of E2 (less than 15 pg/ml), had intermediate levels of PRL. These data suggest that during primate maturation serum PRL levels are dampened by some product of the ovary. Furthermore, whether age specific or environmentally mediated, this rhythm indicates an annual alteration in PRL release, with absolute levels enhanced by E2 replacement after ovariectomy, for prepubertal monkeys housed outdoors. In addition, a significant maturational increase in PRL levels was observed only in INT females when serum levels of PRL were compared for the ages 12-16 months to 24-28 months corresponding to the period between May and September for 2 successive years. These changes in PRL were not related to age-dependent changes in serum E2. Acute treatment of both E2OVX and OVX females with a single injection of E2-benzoate at three different ages did not induce any changes in serum PRL.(ABSTRACT TRUNCATED AT 400 WORDS)