Biology of Reproduction, Vol 11, 413-420, Copyright © 1974 by Society for the Study of Reproduction

The Timing of the Adrenal—Ovarian Interaction Period in the Prepuberal Rat

¹ Department of Physiology, Loyola University School of Medicine, Maywood, Illinois 60153

Our previous reports indicate the existence of a period terminating between 25 and 35 days of age, during which adrenocortical secretions play a role in the maturation of the rat brain—pituitary—ovarian axis (Gorski and Lawton, 1973). In the present study, this period was delineated into an adrenalectomy-induced delay period and a sham-induced advancement period. Animals were bilaterally adrenalectomized at 24-29, 31, and 33 days of age or sham-operated (subjected to ether and laparotomy stress) at 25-35 days of age and autopsied at vaginal opening. All surgeries were performed from 8:00 to 9:00 AM. Adrenalectomy at 24 or 25 days of age significantly delayed vaginal opening but had no effect when performed after Day 25. Laparotomy at 25 and 31-35 days of age had no effect on puberty onset, but when performed at 26-30 days of age puberty was significantly advanced. Days 25 and 26 were, therefore, further investigated by performing treatments at 8:00-9:00 AM and 9:30-10:30 PM on Day 25 and at 1:00-2:00 AM and 8:00-9:00 AM on Day 26. Adrenalectomy at either time on Day 25 and at 1:00-2:00 AM but not at 8:00-9:00 AM on Day 26 delayed vaginal opening. The sham procedure induced an advancement of puberty in the groups treated at either time on Day 26 but not in the groups treated on Day 25. Thus, adrenalectomy performed prior to 2:00 AM on Day 26 delays vaginal opening and laparotomy performed after 1:00 AM on Day 26 until Day 30 advances puberty. In 30/46 control animals, vaginal opening was coincident with the first ovulation; animals laparotomized at any age or adrenalectomized at 27-33 days of age were not different in this respect. In contrast, incidence of ovulation was significantly depressed in animals adrenalectomized at 24-26 days of age. A decreased ova count in estrous animals adrenalectomized up to 28 days of age was also noted. Thus, even when adrenalectomy is ineffective in delaying puberty it interferes with the functioning of the system. Body weights were significantly lower the earlier the animals came into puberty in all groups. Adrenalectomized animals did not differ from either the shams or controls at any age but the shams were smaller than the controls at 34-35 and 38-39 days of age. Uterine and adrenal weights showed no difference among sham groups or between sham and controls. These results demonstrate a definite interaction of the adrenal axis with the maturation and functioning of the reproductive system; removal of adrenal influences at specific times in the developmental period result in a delay in puberty onset and desynchronization of cyclic events.