Abstract
It is postualted that the immature hypothalamic-pituitary unit is more sensitive to inhibition by gonadal steroids and that sexual maturation results from a decrease in this sensitivity. However, we have reported separately tht in the male rat there is no difference in threshold dose of testosterone for feedback inhibition of LH and FSH at the time of sexual maturation. We now wish to report data in the femal rat which provides a possible alternate explanations for puberty. These data indicate that the immature ovary is insensitive to LH stimulation and that this sensitivity is restored by FSH treatment. Hypothalamic-pituitary sensitivity to feedback suppression was tested as in the male. To study ovarian sensitivity to gonadotropin stimulation, immature (21 days) and mature (87 days) females were hypophysectomized. Five days later graded doses of LH (NIH-P7) were administered. Since only LH was administered, specificity of response was not important. Uterine weight increased in mature animals by all doses over 5 μg/100 grams body weight, but was unaffected by doses as large as 2000μg/ grams body weight in immatures. Sensitivity to LH in immatures could be made equal to matures by pre-treatment with FSH. When a contant dose to LH was administered with graded doses of FSH, a dose response to the LH effects was observed. The threshold dose of FSH for ovarian weight increase was similar in matures and immatures and uterine sensitivity to estrogen also was similar. Thus in the female rat FSH induces LH responsiveness of the gonad which in turn results in sexual maturation.
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Odell, W., Swerdloff, R. & Jacobs, H. FSH induction of sensitivity of LH: One mechanishm for control of puberty. Pediatr Res 5, 401 (1971). https://doi.org/10.1203/00006450-197108000-00124
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DOI: https://doi.org/10.1203/00006450-197108000-00124