The Effect of Adrenalectomy on Ovulation and Follicular Development in the Rat

Virgin, female Holtzman rats were used in two experiments. In the first experiment, cycling animals were bilaterally adrenalectomized (ADX) and/or unilaterally ovariectomized (ULO) at 53-57 days of age at metestrus. Rats were allowed to cycle for one estrous cycle and killed at the next metestrus. The second experiment consisted of similar groups, but these animals were allowed to cycle for 30 days before being killed. At autopsy, body and organ weights were recorded; ova were flushed from the oviducts and counted. In the first experiment, ADX rats ovulated fewer eggs per ovary than controls (3.5 ± 0.3 vs. 4.6 ± 0.3). Compensatory ovulation from the remaining ovary occurred in both ADX-ULO (7.4 ± 1.1 eggs per ovary) and ULO (8.7 ± 0.6 eggs per ovary) animals. Similar results occurred in the second experiment. Three animals from each of the four groups in the first experiment were killed at the subsequent proestrus to examine follicular development in the ovaries. Adrenalectomy had no effect on the number of follicles larger than 295 µm but did decrease the number of follicles larger than 448µ m which would normally have been ovulated within that estrous cycle. ADX-ULO and ULO animals had a significant increase in both the mean number of follicles larger than 295 µm and the number larger than 448 µm. Collectively, these data indicate that the absence of the adrenal gland reduced ovulation number, but does not affect compensatory mechanisms in the hemicastrate rat.