Biology of Reproduction, Vol 13, 347-352, Copyright © 1975 by Society for the Study of Reproduction

Effect of Adrenalectomy on Light-Induced Precocious Puberty in Rats

¹ Department of Physiology and Biophysics University of Nebraska Medical Center Omaha, Nebraska 68105, and Department Obstetrics and Gynecology New York Medical College New York, New York 10029

Weanling rats were placed in either a 14:10 cycle (LD) or constant light (LL) and were then left intact, sham-operated or adrenalectomized on the following day. Compared to LD rats, intact and adrenalectomized rats kept in constant light showed a significant advance in the timing of vaginal opening. Compared to intact rats, adrenalectomy delayed vaginal opening by one day in LD (38.1 ± 0.3 days vs. 39.7 ± 0.3, P<0.05) and by three days in LL (32.1 ± 0.7 vs. 36.4 ± 0.2 days, P<0.01). Sham surgery significantly advanced vaginal opening in both LL and LD to the same extent (29.8 ± 1.2 days vs. 29.4 ± 0.2 days, different from intact controls in both cases, P<0.01). There was no rhythm of either progesterone or corticosterone at 25 or 29 days of age in the serum of the rats in LL. By 29 days of age, a progesterone rhythm was evident in intact and sham-operated controls kept in LD but not in adrenalectomized rats. It can be concluded 1) that the adrenal is required for the presence of a progesterone rhythm in the prepubertal rat, 2) that precocious gonadal development, induced by sham surgery, is not dependent upon the presence of a peripheral rhythm of either corticosterone or progesterone or of a daily cycle of light and dark, and 3) the adrenal is not required for the accelerating effect of LL on vaginal opening, although the effect of light on vaginal opening is diminished in the absence of the adrenal.