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- Author: DIANE T. HOLLAND x
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The occurrence of a peak of luteinizing hormone (LH) in the peripheral blood of the sheep within the first 16 h of oestrus is well established (Geschwind & Dewey, 1968; Niswender, Roche, Foster & Midgley, 1968; Goding, Catt, Brown, Kaltenbach, Cumming & Mole, 1969). Changes in the LH releasing hormone (LH-RH) content of the hypothalamus have been correlated with the occurrence of the plasma LH peak and the accompanying decline in pituitary LH content (Crighton, Hartley & Lamming, 1973). Using a radioimmunoassay for LH-RH, Kerdelhué & Jutisz (1972) detected increases in plasma LH-RH content in one ewe 2 days before the LH peak and again from 1 h before the start of the LH peak to 8 h after its end. The present report describes the simultaneous determination of LH and LH-RH in samples taken at frequent intervals from onset of oestrus in the sheep.
Serial blood samples (2·5 ml)
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The purpose of this study was to determine if luteinizing hormone releasing hormone (LH-RH) could be detected in the peripheral blood of the rat on the afternoon of pro-oestrus by the radioimmunoassay described elsewhere (Jeffcoate, Fraser, Gunn & Holland, 1973a; Jeffcoate, Fraser, Holland & Gunn, 1973b).
Female Sprague—Dawley rats, weighing 220–270 g, were maintained in a room illuminated from 05.00 to 19.00 h. The animals were observed for at least two consecutive 4-day oestrous cycles as judged by daily vaginal smears. At various times on the afternoon of pro-oestrus the animals were lightly anaesthetized with ether and rapidly desanguinated by cardiac puncture. Plasma luteinizing hormone (LH) was determined using the radioimmunoassay described by Daane & Parlow (1971) with minor modifications. This utilized purified rat LH for radio-iodination (NIAMD-Rat LH-1–3), NIAMD-Anti-Rat LH serum-1 and a rat LH preparation (NIAMD-Rat LH-RP-1) was used as standard. Serum (1–2 ml) samples were
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The decapeptide luteinizing hormone releasing factor (LH-RF) has recently been isolated, sequenced and synthesized (Schally, Arimura, Kastin, Matsuo, Baba, Redding, Nair, Debeljuk & White, 1971). This has made possible the development of radioimmunoassays for this factor enabling it to be measured in biological fluids in vivo and in vitro.
Two milligrammes of the synthetic decapeptide (Hoechst) were conjugated to 2 mg bovine serum albumin (BSA) using 75 mg 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide in 0·25 ml water (Goodfriend, Levine & Fasman, 1964). After dialysis overnight, 1 mg of the conjugate in 2 ml water, emulsified in Freund's complete adjuvant, was injected into 20 intradermal sites in a white New Zealand rabbit. A blood sample was obtained 8 weeks after this primary immunization and the assay developed using this antiserum.
LH-RF (0·1–1 μg) was iodinated with 125I (0·5–1 mCi) by the chloramine-T technique (5 μg of chloramine-T), specific activities between 100 and 500 μCi/μg being obtained.
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SUMMARY
Autoimmunity to luteinizing hormone releasing hormone (LH-RH) in adult male rats, induced by immunization with LH-RH conjugated to bovine serum albumin, resulted in atrophy of the testes and secondary sex organs and aspermatogenesis. Both immunoreactive luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in serum and the pituitary were reduced to low levels compared with those of control animals. It is suggested that antibodies to LH-RH can inhibit the action of endogenous hormone and that LH-RH is, in fact, the gonadotrophin-releasing hormone in the rat, required for the release of both LH and FSH.
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Differences in foetal and adult adrenal function may be due to qualitative as well as quantitative changes in the pituitary corticotrophic stimulus. Pituitary glands from adult and foetal sheep were freshly dissected and stored at −70 °C until extracted at pH 1·5. The extracts were subjected to chromatography on Sephadex G-100 superfine and fractions were assayed by multiple radioimmunoassays directed against the NH2- and CO2H-terminal sequences of ACTH and lipotrophin (LPH). Peaks corresponding to β-melanocyte-stimulating hormone (β-MSH), β-LPH, γ-LPH, β-endorphin and ACTH were identified, with little or no evidence for the presence of α-MSH and corticotrophin-like intermediate lobe peptide. Three peaks of large molecular weight material, A. B and C, were identified and their relative proportions shown to be considerably greater in the foetus than in the adult. The immunoassay profile of peaks A and B suggested that they were 'stem hormones' which could give rise to a family of biologically active peptides. Since the 'family tree' which they engender varies according to the stage of development, it is proposed that the changes in the 'trophic family' may explain the different adrenal responses of the foetal and adult sheep.
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SUMMARY
The pineal indole 5-methoxytryptophol (ML) has been shown to have an antigonadal activity when administered to experimental animals, but data on its normal pattern of secretion have been lacking. Using a new gas chromatography–mass spectrometry assay, the concentration of ML at various phases of the human menstrual cycle has been studied. Daily samples were obtained throughout the month from five women with a normal cycle and two women taking an oral contraceptive. In women with a normal cycle levels of ML were found to be significantly lower in the last third of their cycle; this change was not seen in women taking an oral contraceptive who had low levels throughout the month. The changes in concentration of ML did not correlate with the changes in concentration of gonadotrophins.
