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SUMMARY
The uptake of technetium-99m (99mTc) by the thyroid was measured 15 min after injection using a directional counting technique. The 'washout' of thyroidal 99mTc after intravenous perchlorate injection was quantitated so that separate measurement of the extrathyroidal activity of 99mTc was unnecessary.
In normal subjects the thyroidal uptake was 1·28 ± 0·61% of the administered dose (mean ± 1 s.d.); in primary myxoedema 0·26 ± 0·28%, in simple goitre 2·18 ± 2·10%, in thyrotoxicosis 11·0 ± 5·4%, in hypothyroid patients with Hashimoto's disease 4·50 ± 3·70% and in three patients with Pendred's syndrome the mean uptake was 9·3%.
The technique has been evaluated and its advantages as a simple alternative to quantitative scintiscanning are discussed.
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The uptake of technetium as pertechnetate by the thyroid is currently accepted as a useful index of thyroid function (Alexander, Harden & Shimmins, 1969). Although Pitt-Rivers & Trotter (1953) have shown thyroidal radioiodide concentration in the colloid using autoradiography, the intrathyroidal site of technetium concentration has not been determined previously.
In this paper, we report the results of autoradiographic studies with [99Tc] pertechnetate in rat thyroid using a method which prevents diffusion of soluble radionuclides until exposure to the autoradiographic emulsion is completed.
Four Sprague—Dawley albino adult male rats were used initially. Two rats received aminotriazole (0·1%) in their drinking water for 3 weeks before the study; the other two rats were on a normal diet. [99Tc]pertechnetate (300 μCi) was administered i.p. to each animal and after 1 h one animal in each group received 10 mg sodium perchlorate by the same route. Ninety minutes
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SUMMARY
5-Methoxytryptophol, a serotonin metabolite, was measured by gas chromatography–mass spectrometry in pineal glands, plasma and control tissues (cerebral cortex and salivary glands) from male rats kept in a controlled lighting environment. In the pineal gland the level of 5-methoxytryptophol was significantly higher during the dark period than during the light, the absolute levels being an order of magnitude less than those of melatonin. In the plasma, the levels showed a reverse situation with respect to lighting conditions. No correlation was found between the 5-methoxytryptophol levels in plasma and the pineal gland in individual animals. These results suggest that there is no obvious correlation between pineal content and pineal activity. This may be due to a combination of rapid turnover, secretion and/or peripheral conversion of another 5-methoxyindole to 5-methoxytryptophol.
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SUMMARY
5-Methoxytryptophol (ML) is found in the pineal gland and is known to have biological activity especially as an antigonadotrophic agent, but methods have been lacking for its measurement in the circulation. A gas chromatography–mass spectrometry assay using a trimethylsilyl derivative has been developed for the routine measurement of ML in plasma. The assay is of great specificity and has a sensitivity of 20 pmol/l. Studies on the levels of pineal indoles in the circulation, however, have been hampered by the possibility that extraneous compounds are being cross-measured. Thus the specificity of the routine assay has been further validated by comparing it with an alternative assay system where all the major parameters were changed, i.e. derivatizing reagent, internal standard and mass number. Results that were obtained using both assay systems were closely comparable.
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Pineal indoles have been shown to affect the release of anterior pituitary hormones but details of the interrelationships are lacking. Using a new gas chromatography–mass spectrometry (g.c.–m.s.) assay the concentration of 5-methoxytryptophol (ML) was measured in plasma samples obtained from 16 children undergoing investigation of pituitary function for delayed growth. All the children received an insulin tolerance test (ITT) to study their endocrine response to stress. Some children received luteinizing hormone releasing hormone (LH-RH) and/or thyrotrophin releasing hormone (TRH). The change in concentration of ML during an ITT was similar to the change in concentration of blood sugar; a drop at 20 min followed by a rise at 30 min. This was not significantly altered by the administration of LH-RH or TRH, nor was there a different pattern of response in children who were deficient in growth hormone as opposed to those with idiopathic delayed growth. The fall in concentration of ML with stress may mediate the increased secretion of pituitary hormones. Alternatively, the pineal gland may respond directly to insulin.
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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.
