Comparison of 16-Androstene steroid concentrations in sterile apocrine sweat and axillary secretions: Interconversions of 16-Androstenes by the axillary microflora—a mechanism for axillary odour production in man?

Abstract

The concentrations of five 16-androstene steroids were determined, by a GC-MS method, in freshly-produced apocrine sweat (adrenaline-induced), in 8 men and 2 women. The ranges of concentrations (nmol/μl) in apocrine sweat were: 5α-androst-16-en-3-one (5α-A), 0.1–2.0 and 4,16-androstadien-3-one (androstadienone), 0–1.9. 5,16-Androstadien-3β-ol (androstadienol) was also found in 5 of the subjects (range 0.05–1.05). 5α-Androst-16-en-3α- or 3β-ols [3α(β)-androstenols] were only found in small amounts (<0.1 nmol/μl) in a few subjects. In the second study, prior to apocrine sweat collection (adrenaline injection), the axillary skin of 6 of the male subjects was washed with diethyl ether on an adjacent site of the axillary vault. The concentrations of 16-androstenes were compared in the ethereal extracts and apocrine sweat. The former contained detectable levels (pmol/cm 2) of androstadienone (17.9±2.4), 3α-androstenol (6.9±3.7), 3β-androstenol (1.8±1.0) and androstadienol (1.9±0.5) (means ± SEM) in all 6 subjects. All but 1 subject also had 5α-androstenone, the mean value for the other being 2.5±0.6. The axillary skin levels of 3α- and 3β-androstenols, androstadienol and, in 3 subjects, androstadienone exceeded those in the apocrine sweat obtained from the same subjects, whereas levels of 5α-androstenone in the skin extracts were all lower than in apocrine sweat samples, when related to the corresponding areas of skin sampled. The metabolism of 16-androstenes was studied in vitro in the presence of two aerobic coryneform bacteria, previously shown to metabolize testosterone as well as being capable of producing odour from extracts of axillary sweat in an odour-generation test. Although both coryneforms caused complex metabolic reactions and were capable of oxidation or reduction at C-3, and C-4, the overall direction favoured reduction. For example, large quantities of the more odorous 5α-androstenone and 3α-androstenol were formed from androstadienol and androstadienone. In contrast, strains of corynebacteria, unable to produce odour and incapable of metabolizing testosterone, were also unable to metabolize 16-androstenes. We propose that, even without the de novo synthesis of odorous 16-androstenes by axillary bacteria, the small quantities of these steroids, including the weakly odorous androstadienol, present in adrenaline-induced apocrine sweat, could be converted by aerobic coryneform bacteria, resident on the axillary skin surface, to a more odorous mixture of 16-androstenes, such that the human olfactory threshold of perception would be exceeded.