Steroid metabolism by rat nasal mucosa: studies on progesterone and testosterone.

The metabolism of [4-14C]progesterone and [4-14C]testosterone by slices of the nasal mucosa from rats was studied. As shown by gas chromatography-mass spectrometry there was a preferential formation of reduced progesterone-metabolites (5 alpha-pregnane-3,20-dione, 3 alpha- and 3 beta-hydroxy-5 alpha-pregnane-20-one, 20 alpha- and 20 beta-hydroxypregn-4-en-3-one, 2 alpha,3 alpha-dihydroxy-5 alpha-pregnane-20-one, 3 alpha,16 alpha-dihydroxy-5 alpha-pregnane-20-one) and reduced testosterone-metabolites (4-androstene-3,17-dione, 5 alpha-dihydrotestosterone, 3 alpha-hydroxy-5 alpha-androstane-17-one, and 5 alpha-androstane-3 alpha, 17 beta-diol, 2 alpha-hydroxy-5 alpha-dihydrotestosterone, 5 alpha-androstane-2 alpha,3 alpha, 17 beta-triol) indicating the presence of 5 alpha-reductase, 3 alpha-, 3 beta-, 17 beta-, 20 alpha- and 20 beta-hydroxysteroid oxidoreductase activities in this tissue. Progesterone-metabolites hydroxylated at positions 2 alpha, 6 alpha, 6 beta, 15 alpha and 16 alpha and testosterone-metabolites hydroxylated at positions 1 beta, 2 alpha, 6 beta, 15 beta and 16 alpha were also identified, indicating the presence of several steroid hydroxylases in the nasal mucosa. Autoradiography of the nasal region of rats injected with [4-14C]progesterone or [4-14C]testosterone showed a selective localization of radioactivity in the mucosa covering the olfactory region of the nasal cavity.