Sex differences in pituitary LH storage and release in LHRH-stimulated pubertal rats. A correlative immunohistochemical and radioimmunoassay study.
This study investigates the relationship between pituitary LHRH responsiveness and the depletion of LH in pubertal rats. The anterior pituitaries of 7-week-old rats of both sexes were stimulated for a maximum of 24 h with either a continuous, or pulsatile exposure to LHRH in vitro. Immunohistochemical examination revealed that most LH-cells in females became depleted of immunoreactive material, regardless of the mode of LHRH administration. In contrast, the majority of LH-cells in the male gland retained a strong immunostaining intensity. Radioimmunoassay showed that the initial pituitary LH content was significantly lower in the female rats (P less than 0.001), but, even so, they released a higher percentage of stored LH in response to LHRH stimulation in vitro. A similar result was also obtained after a single injection of LHRH in vivo. Thus, the lower LH content and higher LHRH responsiveness of the female pituitary explain why LHRH treatment induced a pronounced LH depletion in this sex. These results are discussed in relation to available data on heightened LH secretion in maturing female rats.
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Watanabe
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D066298:In Vitro Techniques; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D010902:Pituitary Gland / Q000032:analysis / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D012727:Sex Characteristics; D012741:Sexual Maturation / Q000187:drug effects; D013194:Staining and Labeling; D013997:Time Factors
D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone