Kristen B. Eik-Nes

Production and effects of 7α-hydroxytestosterone on testosterone and dihydrotestosterone metabolism in rat testis

1. Testicular 7 alpha-hydroxylation of testerone was assayed in cell extracts of rats between 12 and 79 days of age. Maximal 7 alpha-hydroxylase activity was observed about 60 days, while insignificant activity was obtained prior to 42 days of age. 2. 7 alpha-Hydroxytestosterone, a major metabolite of testosterone in mature rat testis, inhibited 5 alpha-reduction of testosterone in cell extracts of mature but not of immature rat testis. 3. Maximal testicular activity of 3 beta-hydroxysteroid dehydrogenase using dihydrotestosterone as substrate was obtained in the presence of NAD, while maximal 3 alpha-hydroxysteroid dehydrogenase activity was observed with NADP. Both enzyme activites were reversible. 4. Sensitivity toward testosterone inhibition of 3-hydroxysteroid dehydrogenase varied greatly with stage of testis development being highest at 25-27 days of age. In contrast to testosterone, 7 alpha-hydroxytestosterone was an inhibitor of 3 alpha-hydroxysteroid dehydrogenase only. In the mature rat testis 7 alpha-hydroxytestosterone may be a naturally occurring inhibitor of dihydrotestosterone and 5 alpha-androstane-3 alpha, 17 beta-diol formation.

Biphasic effect of testosterone propionate on Sertoli cell secretory function.

When various doses of testosterone propionate (10 to 10,000 mug/day) were given to 21-day-old rats for 10 days a biphasic effect was seen both on testis weight and production of androgen-binding protein (ABP). At low doses (10 to 100 mug testosterone propionate/day) there was a reduction in testis weight as well as ABP content in the epididymis. At higher doses of testosterone propionate, there was a stimulation of both testicular weight and ABP production in spite of suppressed serum FSH and LH levels. These effects of testosterone propionate on Sertoli cell secretory function strongly suggest that the Sertoli cell is a target cell for androgen.

Biochemical studies of rat lung following exposure to potassium dichromate or chromium-rich welding fume particles

Rats were examined for biochemical changes at the lung surface and in lung tissue 1, 4, and 13 weeks after a single instillation of the soluble of insoluble fraction of stainless steel welding particles, or potassium dichromate containing concentrations of hexavalent chromium (CrVI) equivalent to those found in the welding particles. Most of the toxicity of the welding particles 1 week after instillation could be related to the content of soluble CrVI, though the insoluble particles also produced changes at the alveolar surface. The regression of inflammatory changes 4 and 13 weeks after instillation was probably due to the removal of soluble components such as CrVI from the lung.

Circulating Steroids in Male Rats Following Inhalation of n-Alcohols

The effect of inhaled methanol, ethanol, n-propanol and n-butanol on male reproductive function as measured by the serum concentration of circulating T (testosterone) and LH (luteinizing hormone) has been investigated. The animals were exposed to concentrations of these alcohols equal to the current threshold limit values in industry (methanol: 200 ppm, ethanol: 1000 ppm, n-propanol, n-butanol: 50 ppm) 6 h a day for up to 1 week. A significant depression in the concentration of circulating T was found after the first 6 h exposure to the respective alcohols with restoration after a recovery period of 18 h, except in rats exposed to n-butanol where a depression of 48% could still measured. The concentration of LH was within the normal range in all experimental groups whereas corticosterone was increased after exposure to n-butanol. Exposure for 1 week was not associated with any significant inability of the rat testis to produce T.

Androgen metabolism in rat skeletal muscle in vitro

Androgen metabolism by the cytosol fraction of rat skeletal muscle was investigated. Testosterone metabolism was low, the main metabolite being 4-androstene-3 alpha,17 beta-diol. In addition, small amounts of 5 alpha-androstane-3 alpha, 17 beta-diol were formed, but no 17 beta-hydroxy-5 alpha-androstane-3-one could be detected. 4-Androstene-3 alpha,17 beta-diol was metabolized only to testosterone in this system of incubation. When 17 beta-hydroxy-5 alpha-androstane-3-one was incubated with muscle cytosol, considerable metabolism to 5 alpha-androstane-3 alpha,17 beta-diol and to 5 alpha-androstane-3 beta,17 beta-diol could be detected. Low 5 alpha-reduction of testosterone and rapid conversion of formed 17 beta-hydroxy-5 alpha-androstane-3-one to 5 alpha-androstane-3 alpha,17 beta-diol and 5 alpha-androstane-3 beta,17 beta-diol gave limited ability of the muscle preparation employed to accumulate 17 beta-hydroxy-5 alpha-androstane-3-one.

Androgen receptor specificity and growth response of a human cell line (NHIK 3025)

Abstract Growth of cultured NHIK 3025 cells stemming from a carcinoma of the human uterine cervix can be stimulated by the androgens 4-androstene-3β,17β-diol and testosterone, but is not influenced by oestradiol. In the cytosol fraction of these cells testosterone and 5α-dihydrotestosterone could be bound specifically to a steroid receptor with limited capacity (8 fmol/ mg cytosol protein), but no specific binding of oestradiol or of the synthetic progestagen R-5020 could be demonstrated. The specificity of the binding was studied by agar-gel electrophoresis and sucrose density gradient centrifugation. In the cytosol no specific binding of 4-androstene-3β,17β-diol could be demonstrated and addition of this steroid to cytosols containing [ 3 H]testosterone did not interfere with [ 3 H]testosterone binding. Receptor-bound steroid could be extracted from the nuclei after incubation of intact NHIK 3025 cells with 3 H-labelled 4-androstene-3β,17β-diol, testosterone or 5α-dihydrotestosterone. However, considerable metabolism of 4-androstene-3β,17β-diol occurred and the radioactivity recovered from the bound fraction represented mainly testosterone and 5α-dihydrotestosterone. In addition to the androgen receptor the NHIK 3025 cells also contain a glucocorticoid receptor (190 fmol [ 3 H]dexamethasone bound/mg cytosol protein).

Effects of fixing and staining on images of tropomyosin Mg-paracrystals

Tropomyosin Mg‐paracrystals have been studied by positive and negative staining with uranyl acetate and sodium phosphotungstate, either unfixed or fixed with glutaraldehyde. Fixation causes changes in some of the paracrystal bands. Some of the bands are more intense when a positively‐charged staining ion is used than when a negatively‐charged ion is used, in both negative and positive‐staining techniques. This result rules out the suggestion that negative staining is not affected by the charge of the stain in tropomyosin, and agrees with findings in other specimens. Therefore it is unlikely that any simple parameter based on residue size can be used to predict the image intensity from the amino acid sequence for tropomyosin. These staining patterns cast doubt on the earlier interpretation of a prominent white band in the paracrystal as an overlap of alpha‐helical molecular ends.

Androgen metabolism in relation to growth stimulation by a uterine cell line

The metabolism of radioactive testosterone, 5alpha-dihydrotestosterone, 4-androstene-3beta,17beta-diol or 4-androstene-3alpha,17beta-diol by the human cell line NHIK 3025, derived from a carcinoma of the uterine cervix, was studied. The cells were grown in Eagles minimal essential medium (MEM) with a steriod concentration of 10-(7) M for 4 days. Androgen metabolism by this cell line is essentially the same as for other androgen-responsive cells. The most interesting testosterone metabolite in this system is 4-androstene-3beta,17beta-diol, and the separation of this compound from 4-androstene-3alpha,17beta-diol and the two corresponding 5alpha-reduced diols is described. Since 4-androsterone-3beta,17beta-diol is a more potent growth factor for these cells than testosterone, the small conversion of testosterone to 4-androstene-3beta, 17beta-diol observed could be responsible for the growth stimulation by testosterone.

Metabolism of 5α-androstane-3β,17β-diol to 17β-hydroxy-5α-androstan-3-one and 5α-androstan-3α,17β-diol in the rat

Abstract Significant metabolism of 5α-androstane-3β,17β-diol to 17β-hydroxy-5α-androstan-3-one was recorded in several tissues and organs from rats and humans. This bioconversion was further investigated in rat testis homogenates. 5α-Androstane-3β,17β-diol was readily metabolized to 17β-hydroxy-5α-androstan-3-one with NAD and/or NADP added as cofactors. When a NADPH generating system was included in the incubation, 5α-androstane-3β,17β-diol was metabolized to 5α-androstan-3α,17β-diol. Only small amounts of 17β-hydroxy-5α-androstan-3-one accumulated under the latter condition.

Biochemical and cytological studies of rat lung after inhalation of methanol vapour

Rats were examined for changes at the lung surface and in lung tissue after inhalation of methanol vapour for up to 6 weeks at doses of up to 10 000 ppm. No significant changes were found in any of the parameters measured. Methanol vapour therefore does not appear to exert appreciable toxicity at these exposure levels towards rat lung.