Specific LH and FSH Bio-assays in Rats with Hypothalamic Lesions and Accessory Sex Gland Hypertrophy1

Abstract

Anterior hypothalamic lesions produce accessory sex gland hypertrophy in male rats. We have examined gonadotrophin secretion in such animals by means of specific bio-assay for LH and FSH. In one experiment, lesion placement was followed, 42 days later, by seminal vesicle and ventral prostate enlargement and depletion of pituitary LH concentration and content. In both control and lesion-bearing rats, plasma LH activity was undetectable. In another experiment, the effects of similar lesions were studied, 10 and 49 days postoperatively, in castrates (orchidectomized at the time of lesion placement) as well as in rats with intact testes. In the latter groups, lesions had increased only ventral prostate weight by the 10th day but produced marked enlargement of both accessories by the 49th day. This progressive hypertrophy suggests that the functional alteration was sustained. Although accessory sex gland responses were comparable in both experiments, bioassay findings diverged. In the second, the lesions did not alter pituitary LH (or FSH) concentration detectably. As before, plasma LH was undetectable in noncastrates. Castration produced marked changes, which lesions did not appear to modify. Plasma LH was comparable, in rats with and without lesions, 10 days after castration (4.4 vs. 3.7 μg/100 ml). By 49 days, it was high in both groups (13 vs. 14 μg/100 ml). Pituitary LH concentration was increased 8-fold in both groups by the 49th day (although neither group showed a significant increase at 10 days). Pituitary FSH concentration was changed neither by lesions, castration, nor the combination thereof. The bearing of these findings on the problem of explaining the sustained effect of these lesions on male accessory sex gland growth is discussed. (Endocrinology74: 114, 1964)