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Search for other papers by MRIDULA CHOWDHURY in
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SUMMARY
Levels of LH and FSH were measured by radioimmunoassay in serum, pituitary and placental tissues of male and female foetal and newborn rats. No gonadotrophins were detected in placental tissues or amniotic fluid. In the male, pituitary FSH and LH were first detected on day 17 of gestation. Gonadotrophins could not be detected in any female tissues until birth. In male foetuses the highest levels of both LH and FSH in the circulation were found on day 16 of foetal life; subsequently the levels decreased dramatically.
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Oestrogens cause atrophy of the testes and accessory sex organs, a decrease in pituitary gonadotrophins (Greep, 1961; Price & Williams-Ashman, 1961), and suppress gonadotrophin secretion in gonadectomized males (Gay & Dever, 1971). Since gonadotrophins are essential for stimulation of androgen production, atrophy of the accessory sex organs has been attributed to lack of testosterone production by the testes secondary to decreased circulating luteinizing hormone (LH) (Moore & Price, 1932). These assumptions served as the basis for interpreting results in an investigation of the pituitary-gonadal system (Steinberger, 1971). Experiments reported here were designed to test these assumptions.
Male, adult, hooded rats (250–300 g) were used. Experimental animals were injected daily with 50 or 500 μg oestradiol benzoate (OB), s.c. in 0·1 ml sesame oil, and groups of six animals were killed 24 h and 7 days after initiation of treatment. Luteinizing hormone was measured by double-antibody radioimmunoassay (Steinberger, Chowdhury & Steinberger, 1973)
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During the biosynthesis of rat LH (rLH) there are four molecular species found intracellularly: native rLH, a species which co-elutes with rLHα on Sephadex G-100, a species which elutes with an apparent molecular weight of approximately 21 000 and a large molecular weight form (excluded from Sephadex G-100). Significant quantities of native rLH and rLHα are secreted. The species of large molecular weight binds to Concanavalin A–Sepharose suggesting that it is glycosylated. The 21 000 molecular weight rLH-like molecule has tentatively been identified as an rLH subunit which has not been completely processed.
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Program in Reproductive Biology and Endocrinology, University of Texas Medical School at Houston, Houston, Texas 77025, U.S.A.
(Received 21 May 1974)
The atrophy of testes and sex accessories in adult male rats, associated with a decrease in pituitary gonadotrophin levels after oestrogen administration, is well established (Greep, 1961; Price & Williams-Ashman, 1961). Since gonadotrophins stimulate androgen production and secretion by the testes, atrophy of the sex accessory organs in oestrogen-treated animals is attributed to diminished testosterone production, secondary to low levels of luteinizing hormone (LH) in the blood (Moore & Price, 1932). However, recent studies have shown that oestrogen administration for relatively short periods of time causes a decrease in the sex accessory weights but the serum LH levels remain unchanged (Mallampati & Johnson, 1973; Chowdhury, Tcholakian & Steinberger, 1974). In addition, the oestrogen treatment produces a rapid decrease in testicular (Chowdhury et al. 1974) and plasma (Danutra, Harper, Boyns,
