Pituitary and Plasma LH of Ovariectomized Rats with Median Eminence Implants of LH

Abstract

The effect of im-plantation of LH [luteinizing hormone] into the median eminence (ME) area of ovariectomized rats on pituitary and plasma LH was investigated. Eight to 10 days following implantation, the animals were sacrificed and LH was determined according to the Parlow method. Three identical but separate ME + LH experiments were performed. In each exper-ment, the ME + LH animals demonstrated a consistently and significantly lower pituitary LH content, when compared to either the unim-planted, or sham-implanted, ovariectomized controls (minimum average % depression of ME + LH rats =33.3; range =32-46). Plasma LH of the ME + LH group was not significantly reduced. The results indicate though, in view of the absence of the ovarian steroids, that LH may play a role by itself in the negative feedback control of its hypothalamic regulator.