Hypersecretion of Follicle-Stimulating Hormone (FSH) after Ovariectomy of Hypophysectomized, Pituitary-Grafted Rats: Implications for Local Regulatory Control of FSH

Previous observations have shown that a portion of the acute (>12 h) FSH hypersecretion after ovariectomy (OVX) is LHRH independent, thereby suggesting that mechanisms governing the acute FSH hypersecretory response to OVX may reside largely within the anterior pituitary gland. Accordingly, the present studies were conducted to determine whether acute OVX-induced FSH hypersecretion can be elicited in an animal model in which the anterior pituitary gland is isolated from diencephalic chemical signals, and if so, whether the hypersecretion could be abated by the FSH-suppressing protein, follistatin. Adult female rats hypophysectomized (H) 1 week earlier received anterior pituitary grafts (H/G) (one to three glands per rat) under the kidney capsule. In order to increase ovarian secretion of negative feedback effector substances (i.e. estrogen, inhibin), some H/G rats were injected sc with 30 IU PMSG 4-6 days after receiving pituitary transplants, whereas Other rats were given the saline vehicle. Two days lat...