Special uses of a gas chromatograph-mass spectrometer in endocrinology
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Isotope dilution
The paper reviews the applications that the gas chromatography and the derivatization gas chromatography in food analysis for the past many years.And it elaborated introduces the applications of gas chromatography-mass spectrometry(GC/MS) methods in analysis of fatty acids,saccharide and vitamin for the past few years.
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Aromatization
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Electron capture detector
Electron capture
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P450 2C11 from rat liver is known to metabolize testosterone to 2 alpha-, 16 alpha-, and 6 beta-hydroxytestosterone, and to androstenedione and 16 alpha-hydroxyandrostenedione. Because Waxman (J. Biol. Chem. 259, 15481-15490) has reported that the enzyme converts androstenedione to 16 alpha-hydroxyandrostenedione, it seemed likely that the metabolite was formed from testosterone by way of androstenedione. Indeed, we have found that P450 2C11 does not convert 16 alpha-hydroxytestosterone to 16 alpha-hydroxyandrostenedione to any significant extent and, therefore, that the metabolite is formed from testosterone almost solely by way of androstenedione. To determine whether some of the 16 alpha-hydroxyandrostenedione might be formed directly from the androstenedione-enzyme complex, we developed an approach by which it is possible to calculate the amount of the androstenedione, released into the medium, relative to the amount of the androstenedione-enzyme complex that is converted directly to 16 alpha-hydroxyandrostenedione under initial conditions when the concentration of released androstenedione will be negligible. The approach uses two factors: factor A is the androstenedione/(androstenedione + 16 alpha-hydroxyandrostenedione) present at the end of the incubation, and factor B corrects for the amount of released androstenedione that recombines with the enzyme and is converted to 16 alpha-hydroxyandrostenedione. Although the values of both factors A and B will vary with the concentrations of testosterone and preformed androstenedione present in the incubation mixtures and with the duration of incubation, the value of A*B will be independent of these parameters.(ABSTRACT TRUNCATED AT 250 WORDS)
Alpha (finance)
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Isotope dilution
Hydroxyprogesterone
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Twenty diferent steroids, labelled with two to four deuterium atoms have been synthesized according to simple procedures. Labelling techniques have been adapted or modified to make them more efficient for the production of internal standards with high isotope enrichments. The stability of the carbon–deuterium bonds has been checked according to the following criteria: storage time in non-protic solvents, incubation in biological samples and derivatization reaction conditions. Care has been taken not to introduce more than four deuterium atoms per molecule, otherwise retention time decrease becomes significant. The limitations of the gas chromatographic mass spectrometric technique for the accurate measurement of the isotope composition of these highly enriched deuterium labelled compounds has been discussed in relation to the existing carrier effect.
Isotope dilution
Accelerator mass spectrometry
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The purpose of this study was to characterize the serum profile of androstenedione during pregnancy in the C3H/HeN mouse and to determine the site of its production. Serum androstenedione levels were characterized by a prominent midpregnancy elevation and were substantially higher than testosterone levels during pregnancy. The results of our studies support a placental site of production for androstenedione during midpregnancy: 1) uterine venous levels of androstenedione are higher than peripheral androstenedione levels at midpregnancy and during the second half of pregnancy, 2) developmental changes in the in vitro release of androstenedione by conceptuses coincide temporally with serum changes in androstenedione levels, 3) the day 10 placenta releases significantly more androstenedione in vitro than do other endocrine tissues from day 10 of pregnancy, and 4) serum androstenedione levels are maintained after bilateral ovariectomy on day 10 of pregnancy. (Endocrinology113: 1408, 1983)
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