Steroids present in the follicular fluid of the mare

Using paper chromatographic techniques, it has been possible to identify the following steroids in the follicular fluid of the mare (results expressed as μg/1.): oestradiol-17β, 460 μg; oestrone, 34 μg; cortisol, 12 μg; progesterone, 124 μg; 17α-hydroxyprogesterone, 66 μg; epitestosterone, 24 μg; androstenedione, 136 μg. In addition to these seven compounds, 136 μg of an unidentified oestrogen-like substance and 52 μg of an unidentified 17-ketosteroid were also present.

This is the first time that epitestosterone has been identified as a natural product, and the possible significance of this compound is discussed. 19-Hydroxyandrostenedione, the postulated intermediate in the formation of oestrone from androstenedione, was not detected in this study, and some doubt is therefore cast on the theory that it is an essential intermediate in the biosynthesis of the ovarian oestrogens.

The presence of relatively large amounts of an unidentified polar oestrogen in follicular fluid suggests that it may be of some physiological significance, although at the present time no information is available on the biological activity of this compound.

The validity of the calculation of secretion rates from the specific activity of a urinary metabolite

The validity of the calculation of secretion rates from the specific activity of a urinary metabolite after the injection of the radioactive hormone (secretion rate equals radioactivity injected divided by the specific activity of a urinary metabolite ) has been critically examined. Although in previous applications of the method the expression has been assumed to be valid on an intuitive basis, it is concluded that this is not justified unless after continuous infusion the specific activity of the hormone is constant throughout the body. In the case of a single injection, where W has been termed the single injection factor, and must be equal to one for the method to be valid. If the transport and metabolism of the hormone can be described in terms of an outer and inner pool, it has been shown that the single injection factor is nearly equal to one unless the metabolite which is analyzed is formed mostly in one pool but the overall metabolism largely occurs in the other space.

Other assumptions and sources of error in the method are discussed. It is concluded that a comparison of the specific activities of various metabolites is the most generally applicable experimental test of the validity of the method. On this basis, applications of the method to obtain the secretion rates of aldosterone and cortisol seem to be justified.

Steroids present in the follicular fluid of the cow

The following steroids have been identified in the follicular fluid of the cow (results expressed as μg./l.): pregnenolone, 3·3 μg.; progesterone, 233·0 μg.; 20β-hydroxy-pregn-4-en-3-one, 23·0 μg.; 17α-hydroxyprogesterone, 37·6 μg.; androstenedione, 31·5 μg.; testosterone, 22·1 μg.; oestrone, 5·4 μg.; oestradiol-17β, 94·0 μg.

It was not possible to detect any cortisol, 19-norandrostenedione, epitestosterone, dehydroepiandrosterone or 6α-hydroxyoestradiol-17β, although each of these steroids has been identified in equine follicular fluid. It therefore seems as if there are qualitative as well as quantitative differences between species with respect to the steroids present in follicular fluid. However, progesterone, 17α-hydroxyprogesterone, androstenedione, oestrone and oestradiol-17β are present in bovine, equine and human follicular fluid, and oestradiol-17β is the predominant oestrogen in all three species.

The chemical specificity of the Schultz test for steroids

The colours given by a number of pure steroids under various strongly acid conditions have been studied both in the test tube and in model sections prepared in various ways. Aqueous sulphuric acid solutions containing ferric ions were found to give an intense blue-green colour with steroids closely related chemically to testosterone, and colours in the pink-mauve range with certain other steroids such as the oestrogens and pregnenolone. The blue-green colour has two sharp absorption bands in the red which make possible the conclusive identification of the testosterone group of compounds. A new modification of the Schultz reaction has therefore been devised: frozen sections of formalin-fixed material are mounted on slides, blotted dry, treated with a drop of 80% aqueous sulphuric acid containing 0.5% iron alum and the resulting colours observed. This procedure has several advantages over previous modifications: there is no charring and very little cytological distortion; the colours are stable for many hours, and their chemical specificity is more clearly defined. Cholesterol itself gives no colour, but preliminary oxidation (e.g. by preincubation in iron alum) leads to the formation of the typical blue-green colour. Various aspects of this new histochemical modification of the Schultz reaction are discussed.

delta5 3beta-Hydroxy steroids in the follicular fluid of the mare

A pool of 500 ml. normal equine follicular fluid was examined for the presence of Δ5 3β-hydroxy steroids. Neither pregnenolone nor 17α-hydroxypregnenolone could be detected (< 1 μg./l.), but there appeared to be a small amount of dehydroepiandrosterone (DHA) present (8 μg./l.). These findings suggest that in the Graafian follicle of the mare the conversion of pregnenolone to progesterone normally proceeds fairly rapidly, and the pregnenolone → 17α-hydroxypregnenolone → DHA → androstenedione pathway is probably of minor importance.