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The submicrosomal localization of enzymes involved in androgen and 16-androstene biosynthesis in rat and boar testis tissue has been studied. 16-androstene production was not evident in the rat testis but two enzymes concerned with androgen generation (17 alpha-hydroxy C21 steroid C-17,20 lyase; 17 beta-hydroxysteroid dehydrogenase, were found predominantly in agranular microsomes. In the boar testis the C-17,10 lyase had a similar distribution to the rat enzyme but the 17 beta-hydroxysteroid dehydrogenase was found to be evenly distributed between the two microsomal types. The enzyme system, "andien-betha synthetase", involved in the conversion of pregnenolone to 5,16-androstadien-3 beta-ol, was found mainly (66%) in the agranular microsomes but had a lower specific activity than those of the two enzymes of androgen biosynthesis that have been studied.

The presence of receptors to the "boar taint" pheromones 5alpha-androst-16-en-3-one and 5alpha-androst-16-en-3alpha-ol has been demonstrated in sow olfactory mucosa. Binding studies indicated that a sufficiently low concentration of olfactory tissue homogenate exhibited saturation of binding of 5alpha-androst-16-en-3-one, and this was of high affinity compared with control tissues of non-olfactory and heated olfactory tissues. Analysis of receptor binding of 5alpha-androst-16-en-3-one gave a value for the affinity constant (Ka) of approx. 8.3-10(8) M-1 and the value for the molar concentration of binding sites (n[M]) was approx. 3.3 pmol/mg protein. Almost identical values of Ka and n [M] were obtained when receptor binding of 5alpha-[5alpha-3H]androst-16-en-3alpha-ol was investigated (Ka 8.4-10(8) M-1; n [M] 3.7 pmol/mg protein). This suggests that the same receptor binds both 5alpha-androst-16-en-3-one and 5alpha-androst-16-en-3alpha-ol with equally high affinity. In a preliminary investigation to establish the specificity of the receptor, the binding of 17beta-hydroxy-5alpha-androstan-3-one was assayed; this steroid is odourless but has a similar structure except in ring D to 5alpha-androst-16-en-3-one. Binding was of the low affinity, non-specific type only, indicating that the sow olfactory receptors are not sensitive to this androgen.

Twenty authentic steroids, derivatized as O-methyl oximes (MO), trimethylsilyl (TMS) ethers or as MO-TMS ethers have been subjected to capillary gas chromatography using two different columns. Virtually all of the steroid derivatives have been resolved, one difficult pair to separate being 5,16-androstadien-3 beta-ol and 5 alpha-androst-16-en-3 beta-ol on the non-selective phase OV-1. Where syn and anti forms of MO derivatives arose, these were also resolved under the conditions utilised. This technique of 'steroid profiling' has been applied to the separation and quantification of metabolites of pregnenolone which were formed during incubations of the microsomal and cytosolic fractions from rat testes. The majority of the metabolites were found in the microsomal incubation. These compounds included some odorous 16-androstenes as well as other C21 and C19 steroids, the formation of which was consistent with the 5-ene and 4-ene pathways of testosterone biosynthesis being operative. In addition, evidence was obtained for 16 alpha-hydroxylation of C21 steroids. Very much less metabolic activity was found in the cytosolic fraction of rat testes. Metabolic pathways have been proposed which both confirm and extend earlier work. We conclude that the rat testis can only form some of the odorous, possibly pheromonal, 16-androstenes and that these are quantitatively less important than in the porcine testis.