Distribution of hydroxysteroid dehydrogenases in the placentae and foetal membranes of various mammals

The distribution of dehydrogenases acting on 3α-, Δ5-3β-, 3β-, 11β-, 16β(androgen)-, 16β(oestrogen)-, 17β-, and 20β-hydroxysteroids in the placentae and foetal membranes of the horse, sheep, goat, cat, dog, ferret, rat, rabbit, guinea-pig and man at various stages of pregnancy is described, and some attempt is made to relate their presence in the tissues with their function.

Δ5-3β-Hydroxysteroid dehydrogenase, of particular interest in view of its important function in steroid biosynthesis, was found in the trophoblast of the horse, cat, dog and man, in the thickened maternal endothelium of the ferret placenta, in the trophoblastic giant cells of the rat, and in isolated cells in the uterine lumen of the guinea-pig in early pregnancy. The enzyme was absent from all other sites examined. Correlation is sought between the distribution of this enzyme, the steroid hormone requirements for the maintenance of pregnancy after ovariectomy, and the chemical processes of steroid production by the placentae of the species examined.

Hydroxysteroid dehydrogenase activity in normal human placenta from six weeks to forty-two weeks of gestation

Fifty-two normal human placentae from the 6th to the 42nd week of pregnancy were surveyed for 3α-, 3β-, 6β-, 11α-, 11β-, 12α-, 16α-, 16β-, 17α-, 17β-, 20β-, 21- and 24-hydroxysteroid dehydrogenase (HSD) activities.

Strong NAD-linked 3β-, 16β-, and 17β-HSD activities and moderate NADP-linked 3β-, 16β- and 17β-HSD activities were found in the villous trophoblast at all ages. Weak 3α- and weak or trace 6β- and 11β-HSD activities were found in the trophoblast of some placentae using NAD as cofactor, with no obvious age distribution. Moderate 17β-HSD activity, NAD-linked only, was found in the villous stroma and vasculature.

Histochemical demonstration of 11-beta-hydroxysteroid dehydrogenase

11β-Hydroxysteroid dehydrogenase can be demonstrated histochemically by incubating tissues with nitro blue tetrazolium (2,2′-di-p-nitrophenyl-5,5′-diphenyl-3,3′-(3,3′-dimethoxy-4,4′-diphenylene) ditetrazolium chloride), NAD or NADP and an appropriate steroid. Suitable steroid substrates are: (1) 11β-hydroxyandrost-4-ene-3,17-dione (11β-hydroxyandrostenedione), (2) 3,11β-dihydroxyoestra-1,3,5(10)-trien-17-one (11β-hydroxyoestrone), (3) 3α,11β-dihydroxy-5α-androstan-17-one, (4) 3α,11β-dihydroxy-5β-androstan-17-one and (5) 11β-hydroxypregn-4-ene-3,20-dione(11β-hydroxyprogesterone).

11β-Hydroxysteroid dehydrogenase activity was found in the Leydig cells of six human testes from subjects ranging in age from 12 to 57 yr. with all five substrates.

The Leydig cells of the mouse testis contain demonstrable 11β-hydroxysteroid dehydrogenase activity and the volume of reactive tissue increases regularly between birth and the end of the 10th week of postnatal life; this growth curve is sigmoid in form. An extremely weak histochemical reaction with human placenta obtained at term was observed, 11β-hydroxyandrostenedione being the only substrate utilized to any extent. A specimen of hydatid mole, however, showed intense 11β-hydroxysteroid dehydrogenase activity with all substrates surveyed. 11β-Hydroxysteroid dehydrogenase was also found in the ova, granulosa, theca interna, interstitial tissue and corpora lutea of the mouse ovary.

DEFINITIVE IDENTIFICATION OF MICROQUANTITIES OF RADIOACTIVE STEROIDS BY RECRYSTALLIZATION TO CONSTANT SPECIFIC ACTIVITY

Studies of steroid metabolism using isotopically-labeled compounds at physiological levels present unique problems in the identification of the metabolites and in the demonstration of their radiochemical purity. The submicrogram quantities of material available preclude the use of classical identification techniques. The character of the evidence obtained, the advantages and disadvantages of chromatographic and countercurrent distribution methods are discussed. Crystallization to constant specific activity is a recognized method for demonstrating that a substance is not radiochemically impure. Its parameters have never been accurately defined. Its true power is achieved only when it is preceded by extensive purification of the material to be characterized. In this way, the unknown material is first categorized by its migration rate in various solvent systems, and then by its crystalline identity with the carrier compound. The likelihood of two dissimilar steroids being both isopolar and isomorphic is held to be remote. Liquid scintillation spectrometry and gravimetry are the techniques used for the determination of constant specific activity. This method for measurement of radioactivity is extremely flexible, sensitive, and lends itself to dual-isotope experiments. Gravimetry under standardized conditions is suitably precise and much more generally applicable than spectroscopic quantitation. The parameters of the technique of rapid, forced microcrystallization are analyzed. In particular, the problem of contamination of crystals is analyzed in detail, and it is pointed out that classical concepts of purification by crystallization, developed chiefly in connection with ionic inorganic materials, must be modified when applied to nonionic steroid compounds. A mathematical analysis of the errors inherent in this technique indicates that 3 successive crystallizations of a pure radioactive compound should yield values for the specific activity which are within ± 5 % of the average of the 3 values.