Although considerable data exist on differences in physico-chemical properties of labeled and unlabeled compounds, data on isotopic effects on the metabolism of labeled compounds are limited to conflicting studies by Gold and Few. The present study shows that significant isotope effects may occur in the 3H/14C ratio of hormone metabolites in some subjects though not in all. The use of doubly labeled precursors in establishing metabolic patterns is not precluded provided that only deviations beyond the range of these effects are used in drawing metabolic conclusions. Alternatively misinterpretations due to isotope effects may be avoided by repeating the experiments with the isotope labels on the two precursors reversed (14C compound A and 3H compound B in some studies and 3H-compound A and 14C-compound B in repeat studies). Under these conditions real metabolic differences and isotope effects can be readily distinguished.

Cumene hydroperoxide, sodium periodate and iodosobenzene were not able to support aromatization by placental microsomes in the absence of NADPH or molecular oxygen. In the presence of these oxidizing agents and NADPH, aromatase was slowly inactivated. Dithiothreitol (10mM) prevented the loss of aromatizing activity in the presence of these compounds. One function of dithiothreitol may be to protect aromatase by scavenging harmful oxidizing agents.

Estrogen is believed to be biosynthesized from androstenedione in placental microsomes by a multienzyme pathway in which 19-hydroxyandrostenedione and 19-oxoandrostenedione (or the hydrated form) are obligatory intermediates. However, both 19-hydroxyandrostenedione and 19-oxoandrostenedione competitively inhibited aromatization of androstenedione, and all three steroids were shown to be mutually competitive. 19-Hydroxyandrostenedione and 19-oxoandrostenedione also competed with androstenedione for binding sites in the microsomes at 4 degrees C. In confirmation of the work of Hollander (Hollander, N. (1962), Endocrinology 71, 723-728), and of Osawa and Shibata (Osawa, Y., and Shibata, K., (1973), Abstracts of the 55th Meeting of the Endocrine Society, Abstract 116) when androstenedione and 19-hydroxyandrostenedione were incubated together, both were converted to estrogen, but little androstenedione was converted to 19-hydroxyandrostenedione. Considered together, these results are incompatible with the multienzyme pathway. Rather, these results may be explained by aromatization of androstenedione at a single catalytic site via enzyme-bound transition states. Both proposed intermediates are, according to this view, by-products which can also be aromatized.

Incubation of deoxycorticosterone (DOC) with human fecal flora results in the formation of a variety of products depending on the experimental conditions. Fecal flora, diluted 101 to 107, reduced DOC (16 μg/ml) to THDOC which was further metabolized to 3α-pregnanolone. Small amounts of 3α-pregnanolone, in turn, were transformed to pregnandione and 3β-pregnanolone. Another structure, tentatively identified as 20,21-dihydroxy-5-pregnan-3 one (metabolite X) was often formed in yields of 5–10% in the early phases of incubation. These findings were corroborated in experiments using purified THDOC and purified pregnanolone as substrates.

A mixture of 4-14C-delta4-androstene-3, 17-dione and 6,7-3 H-19-hydroxy-delta4-androstene-3, 17-dione was intravenously injected into three women, and the 3H/14C ratios in urinary 19-hydroxyandrostenedione and urinary estrogens were determined. The ratios of 3H/14C in the estrogens were similar to those of the dose, while the ratios in urinary 19-hydroxyandrostenedione were mcuh higher than those of the dose. The fractional conversions of androstenedione to estrone and of 19-hydroxyandrostenedione to estrone are therefore similar. However, little, if any, 19-hydroxyandrostenedione produced during aromatization enters the circulation and mixes with injected 19-hydroxyandrostenedione.

Following the rapid intravenous injection of 14C-cortisol at 9:00 a.m. and 3H-cortisol at 5:00 p.m. of the same day into normal subjects, the metabolites of cortisol were isolated from urine and found to have different specific activities and 3H/14C ratios which differed among the metabolites and were different from the dose. These results indicate that the fraction of cortisol converted to each urinary metabolite changes during a few hours. The generally employed methods for determination of the secretory rate of cortisol rest upon the assumption that such changes do not occur. These changes in metabolism of cortisol may explain the recently documented differences in specific activities of various urinary metabolites often encountered in the determination of the secretory rate.

16α-Hydroxyprogesterone-4-14C and 16α-hydroxypregnenolone-7α-3H were obtained in good yields by microbiological hydroxylation of correspondingly labeled progesterone (21.7 mC/mM) and pregnenolone (1.2 C/mM) by Streptomyces roseochromogenus (ATCC 3347). The 16α-hydroxylase was induced with an unlabeled steroid. Then a trace amount of the labeled precursor was incubated, and the products were chromatographically separated, identified and their radiochemical purity established by isotopic dilution analysis. Since a steroid different from the labeled precursor was used as the inducer, the specific activities of the products are presumed to be the same as those of their precursors. The microbiological preparation of labeled steroid compounds in trace quantities can be generally applied to obtain other presently unavailable labeled steroids having high specific activities.

The daily rate of production of cortisol in humans was determined by a new method and the resulting values were found to be similar to those obtained by a standard method. The new method entails the injection of a known dose of 3H-cortisol into the subjects, followed by collection of urine for one or two days. Those metabolites having the 3α-hydroxy-5β-pregnane configuration were chemically converted to 11β-hydroxyetiocholanolone, which was then isolated, crystallized and its specific activity determined by counting a weighed sample. The daily rate of production of cortisol was calculated from the dose and from the specific activity of derived 11β-hydroxyetiocholanolone. This procedure avoids the use of both enzymatic hydrolysis of the conjugated metabolites and colorimetry. The new method is more rapid, more economical and more precise than existing methods.

Most investigators currently agree that a significant fraction of estradiol-17β is reversibly bound to albumin in human plasma (1–4). However, recent studies from this laboratory have disclosed an increase in the binding of estradiol in the plasma of a group of male patients with cirrhosis of the liver. All these patients had a significantly reduced concentration of albumin in their plasma. If albumin were the major binding protein for estradiol, one would have anticipated a decreased binding of estradiol in the plasma of these patients. In view of the unexpected observation it was inferred that estradiol is bound to a factor other than albumin (5, 6). This communication presents direct evidence for the presence of such a protein in human plasma.

Article1 August 1960ELECTROLYTE METABOLISM AND ALDOSTERONE SECRETION IN BENIGN AND MALIGNANT HYPERTENSIONJOHN H. LARAGH, STANLEY ULICK, VLODZIMIERZ JANUSZEWICZ, WILLIAM G. KELLY, SEYMOUR LIEBERMANJOHN H. LARAGHSearch for more papers by this author, STANLEY ULICKSearch for more papers by this author, VLODZIMIERZ JANUSZEWICZSearch for more papers by this author, WILLIAM G. KELLYSearch for more papers by this author, SEYMOUR LIEBERMANSearch for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-53-2-259 SectionsAboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail ExcerptThe fundamental relationship between intravascular pressure and electrolyte metabolism is poorly understood. The hormones of the adrenal cortex which act to regulate sodium and potassium balance can produce hypertension both in man and in experimental animals.1, 2 The hypertensive state produced by adrenal mineralocorticoids such as desoxycorticosterone is dependent upon administration of adequate amounts of sodium in the diet, whereas the hypertension induced by glucocorticoids such as hydrocortisone differs in that it is less severe, and it is not dependent upon sodium intake.3Aldosterone, though more potent, produces effects on sodium and potassium metabolism similar to those of desoxycorticosterone. Aldosterone...Bibliography1. SelyeHallRowley HCEEM: Malignant hypertension produced by treatment with desoxycorticosterone acetate and sodium chloride, Canad. M. A. J. 49: 88, 1943. MedlineGoogle Scholar2. PereraKnowltonLowellLoeb GAAIARF: Effect of desoxycorticosterone acetate on the blood pressure of man, J. A. M. A. 125: 1030, 1954. CrossrefGoogle Scholar3. 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FerrebeeParkerCarnesGerityAtchleyLoeb JWDWHMKDWRF: Certain effects of desoxycorticosterone, the development of "diabetes insipidus" and the replacement of muscle potassium by sodium in normal dogs, Am. J. Physiol. 135: 230, 1941. CrossrefGoogle Scholar21. CookeSegarCheekColvilleDarrow REWEDBFEDC: The extrarenal correction of alkalosis associated with potassium deficiency, J. Clin. Investigation 31: 788, 1955. Google Scholar22. HildenKrogsgaard TAR: Low serum potassium level in severe hypertension, Am. J. M. Sc. 236: 487, 1958. CrossrefMedlineGoogle Scholar This content is PDF only. To continue reading please click on the PDF icon. Author, Article, and Disclosure InformationAffiliations: New York, N. Y.*Received for publication April 29, 1960.Presented at the Forty-first Annual Session of The American College of Physicians, San Francisco, California, April 4, 1960.From the Departments of Medicine, of Obstetrics and Gynecology, and of Biochemistry, College of Physicians and Surgeons, Columbia University and The Presbyterian Hospital in the City of New York.†This work was supported by a grant from the U. S. Public Health Service (H-1275), the Fleitas Fund and by Mr. Daniel G. Arnstein.Requests for reprints should be addressed to John H. Laragh, M.D., Department of Medicine, Columbia University College of Physicians and Surgeons, Presbyterian Hospital, 620 West 168th Street, New York 32, N. Y. PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetails Metrics Cited bySelecting Optimum Antihypertensive TherapyJohn H. 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ARMSTRONG, M.D., ANNETTE E. FITZ, M.D., LOUIS SCHWARTZ, M.D.Aldosterone AntagonistsProduction of potassium depletion by benzothiadiazine compounds∗On the Influence of Body Water Volume and Potassium Supply on the Aldosterone Excretion in Arterial Hypertension 1RENAL ISCHAEMIA AND HYPERTENSION : A REVIEW OF THE RESULTS OF SURGERYRelation of Aldosterone Secretion to Hypertensive Vascular DiseaseAldosteronism and Arterial Hypertension 1 August 1960Volume 53, Issue 2Page: 259-272KeywordsAldosteroneHospital medicineHypertensionIngestionMedical servicesMineralocorticoidsObstetrics and gynecologyPotassiumSodiumSurgeons ePublished: 1 December 2008 Issue Published: 1 August 1960 PDF downloadLoading ...