Features Of Steroids Research Articles

Molecular Specificity of 5-Androstenediol as a Systemic Radioprotectant in Mice

We compared in vivo radioprotective efficacy of 5-androstenediol (5-AED) to that of ten other steroids: 17α-androstenediol, dehydroepiandrosterone, 5-androstenetriol (AET), 4-androstenedione (AND), testosterone, estradiol, fluasterone, 16α-bromoepiandrosterone, 16α-fluoro-androst-5-en-17α-ol (α-fluorohydrin, AFH), and 16α-fluoro-androst-5-en-17β-ol (β-fluorohydrin). Steroids were administered 24 or 48 hr before, or 1 hr after, whole-body γ-irradiation. Two days after irradiation at 3 Gy, blood elements were counted. In addition, after irradiation at 9–12.5 Gy, survival was recorded for 30 days. The results showed radioprotective efficacy was specific for 5-AED. One other steroid, AFH, demonstrated appreciable survival effects but was less efficacious than 5-AED. AND and AET produced slight enhancement of survival in some experiments. This is the first demonstration that the prophylactic window for survival enhancement by 1 subcutaneous (sc) injection of 5-AED is as long as 48 hr in mice. Moreover, the results indicate that 1 sc injection of 5-AED 1 hr after irradiation is much less effective than 1 injection 24–48 hr before irradiation. Comparing the molecular features of steroids with radioprotective efficacy leads to the following conclusions: 1) these effects are due to interaction with specific receptors, since sc injection of extremely similar molecules with the same physicochemical properties as 5-AED were not radioprotective; 2) the17-hydroxyl group is essential; 3) this group must be in the β configuration in the absence of nearby side groups; 4) a halogen atom at 16 changes the 17-hydroxyl specificity to α; 5) the 3β-hydroxyl group is not essential; 6) addition of a 7β-hydroxyl group is deleterious; and 7) the effects are not due to activation of sex steroid receptors.

Determination of testosterone:epitestosterone ratio after pentafluorophenyldimethylsilyl-trimethylsilyl derivatisation using gas chromatography-mass spectrometry in equine urine.

A highly specific method is described for measuring the testosterone:epitestosterone ratio in equine urine by gas chromatography-mass spectrometry (GC-MS) with stable isotope internal standards. The procedure was based on Serdolit Pad-1 resin extraction, enzymatic hydrolysis, and chemical derivatisation prior to instrumental analysis. The mixed derivatives, 3-trimethylsilyl-17-pentafluorophenyldimethylsilyl ether (3-TMS-17-flophemesyl) testosterone and epitestosterone, were found to have excellent analytical properties. The specificity of the derivatisation method exploits a unique feature of steroids: the selective exchange of the alcoholic flophemesyl ether for the trimethylsilyl ether. The sensitivity and specificity of the mixed 3-TMS-17-flophemesyl derivatives allow adequate determinations of testosterone and epitestosterone, even in urine from mares, in 5 ml samples. The repeatability of testosterone and epitestosterone was 6.2 and 5.7%, respectively, and their reproducibility was in the range of 6.4-8.7%.

Structural Features of Steroids Which Initiate Proliferation of Density-inhibited 3T3 Mouse Fibroblasts

Abstract The ability of cortisol to initiate DNA synthesis and division of density-inhibited 3T3 mouse fibroblasts appears to correlate with its glucocorticoid activity. Steroids which possess high glucocorticoid activity in vivo such as triamcinolone acetonide, dexamethasone, cortisol, corticosterone, and aldosterone stimulated both DNA synthesis and cell division. The relative potency of these active steroids was related to their relative glucocorticoid potency. Deoxycorticosterone had a very slight stimulatory effect consistent with its slight glucocorticoid activity in other tissue culture systems. Steroids which are devoid of glucocorticoid activity such as testosterone, β-estradiol, tetrahydrocortisol, and progesterone did not initiate DNA synthesis or cell division. The only exception to the correlation between stimulatory and glucocorticoid activity was cortisone. Cortisone was inactive; however, its in vivo glucocorticoid activity apparently depends upon its conversion to cortisol. The structural features of the steroids required for initiation of DNA synthesis and cell division were: an 11β-hydroxyl, a 3-carbonyl and/or a 4:5 double bond, and a C-20,21 constituent. The C-17 and C-21 hydroxyl groups of cortisol were not essential for activity; however, activity was reduced in the absence of these substituents. The addition of an α-fluoro substituent at C9 and/or the addition of a methyl or hydroxyl group at C-16, reduced the concentration necessary to bring about a maximal stimulation, but the magnitude of the maximal stimulation was no greater than that observed when cells were treated with cortisol.

THE ACTION OF STEROID HORMONES AT THE CELLULAR LEVEL.

Although the complex series of events which occur when a steroid hormone is administered to a human subject or to an intact animal might reflect a series of completely unre!lated activities, they are more likely to be secondary to a few fundamental actions on the celils of the body and it is with this second concept that research in this field has been directed. There are two particular features of steroids which may be important in determining their mode of action. Firstly, they have oxygen substituents at certain typical positions which readily undergo enzymatic oxido-reduction and could, therefore, act as coenzymes or prosthetic groups of enzymes in reactions involving hydrogen transfer. Secondly, steroids are surface active and interact with hydrophobic surfaces producing energy. If the energy were to be absorbed iby a receptor molecule it could modify the structure and hence the biological activity of that molecule. A less well defined change is associated with the ability of steroids to capture electrons; this has recently been measured by Lovelock, Simmonds and Vandenheuvel (1963) who consider that the high electron affinities of adrenocortical hormones, a property unusual among organic compounds, might indicate their ability to participate in or control biological oxidative processes. Laidler and Krupka (1961) compared the association between the steroid and a receptor with the formation of an activated enzymesubstrate Michaelis complex. Entropy and volume changes during activation of enzymes indicate that structural changes occur in the enzyme molecule and such changes might explain the disturbances of membrane permeability in nerve cells associated with structural changes in acetylcholinesterase. A similar mechanism might account for changes induced by steroids in the permeability of cell structures. In this process parts of the receptor molecules having specific binding properties might be masked, unmasked, created or destroyed; as well as causing a redistribution of bound substrates, an alteration in enzymic properties might result. Kimberg and Yielding (1962) studied the inhibition of pyruvate kinase by oestrogens and related compounds and showed by viscometry and electrophoresis structural changes in the enzyme, without a change in molecular weight. Yielding and Tomkins (1962) have reported a steroid-hormone induced loss of activity of crystalline glutamic dehydrogenase due to disaggregation into subunits functioning as alanine dehydrogenase with an uncovering of pyridine-nucleotide binding sites. These authors have been more concerned to show the possibility of such changes rather than to attach great physiological significance to them. Chemical changes in receptor molecules after association could account for the highly theoretical possibility of the formation of active enzymes from inactive precursors. That the receptor itsel-f could be an enzyme cofactor has been considered by Scott and Engel (1961) who obtained physical evidence for the interaction between steroid hormones and purine dinucleotides. This interaction between hormone and a coenzyme associated with a postulated change in the structure of the coenzyme might abolish its hydrogencarrying function, but there was no experimental evidence for this. Apart from oxido-reductive changes, metabolism of the steroid molecule is not thought to be of physiological importance except as a mechanism for steroid inactivation. However, competition for active sites on enzymes as opposed to association with them could be of importance in influencing steroid metabolism itself. The various theories which have been proposed to explain the action of steroid hormones at the cellular level will be considered under the following headings: 1. Effects on membrane permeability and active transport. 2. Effects on hydrogen transfer. 3. Effects on enzyme induction and protein synthesis.