Abstract
Daily treatment with a GnRH agonist (GnRH-A) rapidly inhibits reproductive functions. In order to evaluate the relative importance of desensitization at the pituitary and the gonadal levels, immature male rats were treated daily with the GnRH-A BuserelinR (5 ug/d in oil) starting at 40 days of life. After 1 day treatment, testicular content of LH receptors and responsiveness to LH stimulation were already markedly depressed. After 4 days of treatment, inhibition of testicular functions was complete, whereas each pituitary parameter tested was affected but not completely inhibited: plasma FSH was significantly decreased and GnRH receptor content reduced by 50%. LH response to GnRH was blunted but not abolished. After 8 days of treatment, all endocrine functions were extensively impaired. Pituitary LH content dropped to values below 5% of those of control rats. In conclusion, it appears that chronic GnRH-A treatment is very effective to arrest sexual maturation in the male rat and that Leydig cell functions are first affected. Pituitary desensitization was characterized by a post GnRH receptor defect of the LH release process and impairment of LH biosynthesis. Thus, inhibition of sexual functions by GnRH-A includes two sites of action in the male rat, a situation which may not be analogous to that of man for which desensitization of testicular functions appears to be less important.
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Aubert, M., Kreuter, R., Rivest, R. et al. DESENSITIZATION OF PITUITARY VERSOS GONADAL SECRETORY FUNCTIONS OF PERIPUBERTAL MALE RATS BY CHRONIC TREATMENT WITH A GnRH AGONIST. Pediatr Res 20, 1185 (1986). https://doi.org/10.1203/00006450-198611000-00072
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DOI: https://doi.org/10.1203/00006450-198611000-00072