Metabolism of 2-hydroxy(4-14C)estradiol by rat liver microsomes

The metabolism of ¹⁴C-labeled estradiol and 2-hydroxyestradiol by rat liver microsomes has been compared under a variety of experimental conditions. An active liver microsomal system as well as NADPH was required to obtain high percentage yields of water-soluble metabolites from both steroids. Spermine stimulated the formation of polar products in both cases but the sex-difference in metabolism observed with estradiol was less marked with 2-hydroxyestradiol as substrate.     

Metabolism of cortisone-4- 14 C by rat lung tissue

The metabolism of cortisone-4-¹⁴C has been studied in male rat lung tissue preparations. Data indicate the presence of 11β-hydroxysteroid dehydrogenase, Δ⁴-5α-reductase, 3α-hydroxysteroid dehydrogenase and 20α-hydroxysteroid dehydrogenase activity in this tissue. Metabolites identified were hydrocortisone, 17α, 20α, 21-trihydroxy-4-pregnene-3, 11-dione and 3α, 17α, 21-trihydroxy-5α-pregnan-11,20-dione.     

Changes in plasma levels of estrone sulfate and estrone in the pregnant ewe around parturition

A method for the extraction, separation and measurement of estrone sulfate and estrone in a single plasma sample is described. The method has been applied to the determination of plasma levels of estrone sulfate and estrone in pregnant ewes over the period 60 hr before to 20 hr after parturition. The study revealed that the plasma levels of estrone sulfate and estrone began to increase about 40 hr before parturition, reached a peak at parturition and then declined rapidly to levels below the sensitivity of the method by 15 hr postpartum. The peak level of estrone sulfate recorded at parturition was 103 pmol (38 ng) per ml of plasma which was approximately 30 times greater than the corresponding peak level of estrone.     

Metabolism of estrone sulfate in the pregnant sheep

The metabolism of ³H-estrone sulfate (³H-E₁S) in 4 pregnant sheep, two injected i.v. and two i.m., has been studied. Intravenously injected ³H-E₁S had a plasma half-life of approximately 8 min, and metabolic clearance rate of approximately 800 ml/min. Using this clearance rate and the previously published mean plasma concentration of E₁S, the estimated production rate of E₁S is between 8.8 nmol (3.3 μg) and 78.2 nmol (29.1 μg) per min from 2-day to 0-day before parturition.Intramuscularly injected ³H-E₁S disappeared from plasma linearly and was completely cleared well within 3 hours. In all cases, whether i.v. or i.m. injected, the main metabolite isolated was ³H-estradiol-17β-3-sulfate, with only a trace amount as ³H-estradiol-17β-3-sulfate.     

Metabolism of (3-(14)C)tryptophan and (2-(14)C)alanine in cattle tissues

In the experiments involving incubation of the liver, brain cortex, muscle and adipose tissues homogenates with [3-14C] tryptophan for an hour 43.2-89.3% of the label was found in proteins, 7.2-47.2%--in lipids, 2.6-9.4%--in CO2. Following incubation of the above-mentioned tissue homogenates with [2-14C] alanine, proteins, lipids and CO2 contain 28.8-49.3%; 22.6-31.9% and 21.6-49.3% of radioactive label, respectively. Radioactivity of lipids synthesized by the homogenates of the investigated tissues from [3-14C] tryptophan and [2-14C] alanine is 23.5-63.5 and 21.1-56.0%, respectively, the radioactivity of CO2 being 1.4-5.1 and 9.3-11.8% of the above-mentioned compounds synthesized from [1-14C] acetate. The results obtained testify to the considerable contribution of [3-14C] tryptophan and [2-14C] alanine to protein synthesis as well as to their involvement in the substrate supply of lipogenesis and energetic processes in various organs and tissues of cattle.     

Metabolism of [4-14C]oestradiol by oestrogen-induced uterine peroxidase

1. An enzyme that catalyses the metabolism and binding of [4-(14)C]oestradiol to protein and to other high-molecular-weight substances in the presence of H(2)O(2) was shown to be absent from the uteri of immature rats and to be induced by physiological doses of oestrogen or pregnant-mare-serum gonadotrophin. 2. The pH optimum, stability to heat and other characteristics of the uterine enzyme system as well as its subcellular distribution were determined. 3. The increase in the ability of uterine preparations to convert [4-(14)C]oestradiol into water-soluble products as a result of oestrogen treatment was accompanied by an increase in peroxidase and NADH oxidase activities and was inhibited by actinomycin D and cycloheximide. 4. The results support the proposal that the increase in peroxidase activity after oestrogen treatment might be part of an adaptive response of the uterus permitting it to bind and inactivate oestrogens and thus limit the duration of their effect upon this target tissue.     

Metabolism of 4-3-H- and 4-14-C-17alpha-ethynylestradiol 3-methyl ether (mestranol) by women.

A mixture of 4-3-H and 4-14-C-mestranol was administered orally to four women. Reactions involving position 4 were no greater than 1.7-3% of the dose as measured by liberation of 3-H into body water. The extent of de-ethynylation in vivo was no greater than 1-2% of the dose as measured by urinary estrone metabolites. Mestranol (0.7 and 0.32% of the dose), 17alpha-ethynylestradiol (6.6 and 11.3%) and 2-hydroxy-17alpha-ethynylestradiol (0.64 and 0.7%) were identified as metabolite aglycons by reverse isotope dilution after Ketodase hydrolysis of the urine from two of the women.     

Metabolism of [4-14C]estrone in hamster and rat hepatic and renal microsomes: species-, sex- and age-specific differences.

The metabolism of [4-14C]estrone (E1) was examined in liver and kidney microsomes of adult castrated male and ovariectomized female hamsters and rats and in neonatal and immature hamster renal microsomes. In castrated male hamster liver microsomes, E1 was metabolized extensively to six major metabolites; 15 beta-hydroxyestrone, 7 alpha-hydroxyestrone, 6 alpha-hydroxyestrone, 6 beta-hydroxyestrone, 2-hydroxyestrone, and delta(9,11)-dehydroestrone, and a nonpolar fraction. Six minor metabolites of E1 were also detected. In contrast, kidney microsomes derived from castrated male hamsters metabolized E1 to mainly 17 beta-estradiol, 2- and 4-hydroxyestrone, 6 alpha-hydroxyestrone, 6 beta-hydroxyestrone and one monohydroxyestradiol metabolite. However, 16 alpha-hydroxyestrone was not detected. A variable, but low amount of estriol was also found. Interestingly, the quantity of 2-hydroxyestrone found in kidney microsomes of the hamster represented 26% of the total amount of metabolites formed, whereas in liver microsomes, only 9% of the overall metabolism resulted in the formation of 2-hydroxyestrone. The ability of kidney microsomes of female ovariectomized hamsters and two different rat strains to metabolize E1 was 5.9- and 9.4-fold lower, respectively, compared to renal microsomes of male castrated hamsters. The onset of oxidative metabolism in newborn hamster kidneys during development was also assessed. The results indicate that the oxidative metabolism of [14C]E1 in renal microsomes of newborn hamsters was 20-fold less than in kidney microsomes of adult hamsters. While catechol E1 metabolites were essentially negligible in hamster kidneys of these ages, it was evident that the conversion of E1 to estradiol via 17 beta-hydroxysteroid dehydrogenase resembles levels seen in the adult animals. Between the age of one and two months, the male hamster kidney exhibited the capacity to metabolize E1 at levels seen in fully mature adult hamsters.     

Preparation and Metabolism of 2-(14C)-cis, trans-Xanthoxin

2-[¹⁴C]-cis, trans-xanthoxin (specific activity 0.26 µCi/µmol)has been synthesized from4-(1', 2'-epoxy-4'-hydroxy-2', 6',6'-trimethyl-l'-cyclohexyl)-trans-3-buten-2-oneand methyl 2-[¹⁴C]-bromoacetate. When 2-[¹⁴C]-cis, trans-xanthoxin was fed to cut shoots of tomatoand dwarf bean, it was converted within 8 h to (+)-abscisicacid in yields of 10.8 and 7.0 per cent respectively. Pea seedsand tomato fruits gave much smaller conversions. A second majormetabolic product extracted from treated tomato and bean shootswas shown to be a metabolite of abscisic acid and has been tentativelyidentified as phaseic acid. These results, together with the earlier finding that xanthoxinis present in the extracts of many seedlings, suggest that xanthophyllsand xanthoxin may be precursors in the biosynthesis of ( + )-abscisicacid     

Metabolism of [4-14C] testosterone in the rat uterus in vitro.

In view of the uterine action of androgens we have investigated in vitro the metabolism of [4-14C]-testosterone in uterine tissue of ovariectomized rats. After purification of the extracts on Amberlite XAD-2 the metabolites have been isolated by gel. Five metabolites were isolated and identified during these incubation studies: 4-androstene 3,17-dione, 17beta-hydroxy-5alpha-androstan-3-one, 5 alpha-androstane-3alpha17beta-diol, 4-androstene-3 beta, 17beta-diol and 4-androstene-3alpha, 17beta-diol. Furthermore, two polar C19O3-metabolites and one isopolar to 5 alpha-androstane-3, 17-dione have also been detected. The metabolites were characterized by radioactive gas chromatogrphy, and determination of the relative specific activity in the eluates of Sephadex column chromatography. The identification of allylic alcohols was complemented by their oxidation to 4-androstene-3,17-dione. The present data show that activity of 17beta,3alpha- and 3beta-hydroxysteroid-oxidoreductase and 5alpha-ring-reductase are involved in the metabolism of testosterone in vitro in the rat uterus. The very low 5 alpha-reductase activity under the experimental conditions used in this work explains the formation of allylalcohols as the principal metabolites of testosterone in the rat uterus.