Biomedical subjects
Publications and source records attributed to E V JENSEN.
Compared with other species, the rat is unusually vulnerable to polynuclear aromatic hydrocarbons. In the rat, relatively small amounts of carcinogenic aromatics (i) profoundly depress incorporation of thymidine in DNA, (ii) greatly induce menadione reductase in liver, and (iii) then kill the rat.
Large doses of 7,12-dimethylbenz[a]anthracene (7,12-DMBA) caused the death of rats within 1 day. A small amount of any of 5 polynuclear aromatic hydrocarbons or of an aromatic amine given before the highly toxic dose of 7,12-DMBA resulted in survival for more than 2 months and the specific atrophy of testis which follows 7,12-DMBA was largely prevented. Among the protective aromatics is 7,12-DMBA itself; a small dose of 7,12-DMBA given in advance induced protection of life against an otherwise lethal dose of 7,12-DMBA but only in a proportion of the animals, and testis was not protected from injury. The highly efficient inducers of protection were condensed aromatics composed of 4 or 5 rings. Protection of life against toxicity of big doses of 7,12-DMBA by pretreatment with small doses of aromatics required time (ca. 5 to 8 hours) for its induction. Ethionine given a few minutes after a highly efficient inducer of protection, 3-methylcholanthrene (3-MC), abolished induction of protection; ethionine given 8 hours after 3-MC exerted no influence on its protective effect. A lethal dose of 7,12-DMBA resulted in a considerable reduction in incorporation of tritium in DNA from tritiated thymidine while at the same time synthesis of menadione reductase was induced in liver. A small dose of 3-MC given prior to 7,12-DMBA was advantageous in partially protecting DNA synthesis.
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Two small groups of steroids in the estrane series-here designated as impeded estrogens,-represent a class of compounds which differ from the majority of estrogenic substances in exerting certain unusual influences on growth of the uterus. The induction of these effects previously was considered to be peculiar to estriol. The unusual growth properties common to impeded estrogens are twofold: (a) after the threshold dosage required to initiate growth has been reached, the slope of the curve of increment of uterine weight in response to increased steroid dosage is very gradual rather than steep; (b) these compounds possess the ability to inhibit to a limited extent the uterine growth induced by estrone administered concurrently. The partial inhibition of estrone-induced growth of the uterus is confined to a critical dosage of the impeded estrogen and is overcome by increased dosage of the inhibitor. Estrone-induced growth of the vagina is not inhibited by impeded estrogens. Furthermore the simultaneous administration of impeded estrogens and testosterone does not lessen the amount of uterine growth evoked by the latter. The impeded estrogens so far encountered are 3-hydroxyestratriene derivatives possessing either a ketone group at position 6 or a hydroxyl group at position 16. Oxygenated functions at these positions in phenolic estrogens have special significance in the excitation and restraint of uterine growth unshared by similar groups at certain other sites of the estrane molecule.
Progesterone, 5-pregnene-3,20-dione, and desoxycorticosterone were found to be partial but significant inhibitors of estrone-induced growth of the uterus of hypophysectomized rats but they did not depress the amount of growth elicited by testosterone. The presence of both the 2-carbon side chain at position 17 and an oxygenated function at position 3 is necessary for the inhibitory activity of progesterone. The introduction of a hydroxyl group in the progesterone molecule at positions 6 (beta), 11 (alpha), 16 (alpha) or 17 (alpha) destroyed its growth-inhibitory activity. 11beta-Hydroxyprogesterone is weaker than progesterone in the inhibition of estrone-induced uterine growth; unlike progesterone it has the capacity to depress growth elicited by testosterone. The introduction of a flourine atom in the 9 (alpha) position resulted in a striking increase of the growth-inhibitory activity of 11beta-hydroxyprogesterone and hydrocortisone. 9alpha-Flouro-11beta-hydroxyprogesterone is a partial but significant inhibitor of growth of the uterus in hypophysectomized rats injected simultaneously with large doses of estrone or testosterone. It is more powerful than progesterone in transforming the vaginal epithelium to mucus cells in the presence of estrone. Administered alone, the only detectable growth was a slight increase in size of the preputial glands. 9alpha-Flouro-11beta-hydroxyprogesterone suppresses in part the growth of the adrenals, ovaries, and uterus in intact rats at a dose level which does not cause loss of body weight or inhibit body growth. Many rats treated with this compound in small amount had extensive mucification of the vagina resembling that of late pregnancy.
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In the hypophysectomized albino rat which is protected from contact with steroids in the ration and environment the uterus and vagina are highly atrophic but are sensitive indicators of activity of substances which promote their growth. Both the pituitary growth hormone and certain steroids have the common property of inducing growth of these tissues. The vaginal epithelium consists of 2 layers of cells which differ profoundly in their growth in response to steroids, depending on the molecular structure of these compounds. The differential response to modifications of chemical structures of steroids permits evaluation of the importance of the intramolecular components for the process of growth. The number and site of functional groups, the geometry of the molecule and the state of oxidation are of high importance in determining physiologic activity of steroids in the androstane series; these features are less specific in the estrane series. Side groups at positions C(3) and C(17) are of importance in the promotion of growth by steroids in the androstane series, but these active centers are not equivalent in their physiological influence. As a generalization, hydrogenation of the oxygen function at C(17) (but not at C(3)) and dehydrogenation at critical areas of the ring structure increase the quantitative efficacy of steroids in promoting growth. The position of double bonds and the state of oxidation at both C(3) and C(17) determine the qualitative type of growth-cellular pattern, which a compound in the androstane series induces in the vaginal epithelium.
The presence of a 17beta-hydroxyl group endows the simple androstane molecule with the ability to produce growth of the uterus, vagina, and prostate of the female hypophysectomized albino rat. It appears that hydrogen atoms at position 17 are of critical importance since related compounds with a ketone group at this site are inactive. Monofunctional steroids with a hydroxyl or a ketone group at position 3 likewise are devoid of activity. If a phenolic A-ring is present in monofunctional steroids the 17beta-hydroxyl group is not obligatory for growth. Proliferation of the uterus and vagina were found to follow the administration of 17-desoxyestradiol.
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