title: Progesterone metabolism in the gastric mucosa microsomes of guinea pig.
abstract: The microsomes from guinea pig gastric mucosa were found to convert [4-14C]progesterone to two major metabolites in the presence of NADPH. The gastric metabolizing activity was the highest among the gastrointestinal tissues of guinea pig. 5 alpha-Pregnane-3,20-dione and 3 beta-hydroxy-5 alpha-pregnan-20-one were identified as the major metabolites by thin-layer chromatography and crystallization to constant specific activity, suggesting the presence of steroid 5 alpha-reductase and 3 beta-hydroxysteroid dehydrogenase activities in the gastric mucosa microsomes. Furthermore, time course of progesterone metabolism and analysis of 5 alpha-pregnane-3,20-dione metabolites suggest that the gastric progesterone metabolism is initiated by 5 alpha-reductase and followed by 3 beta-hydroxysteroid dehydrogenase. The progesterone-metabolizing activity was strongly inhibited by SKF 525-A and disulfiram. The activity was also inhibited by methyrapone to a somewhat lesser extent than the above inhibitors. From gastric mucosa microsomes, the progesterone-metabolizing activity was successfully solubilized with 2% digitonin using 0.1 M potassium chloride and 1 mM dithiothreitol, 0.4 mM NADPH and 20% glycerol as stabilizers for the solubilized activity. Among these stabilizers, glycerol was found to be most effective for stabilizing the activity of the solubilized microsomes.
authors.affiliation: Department of Biochemistry, Kawasaki Medical School, Okayama, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ichihara
authors.forename: C
authors.initials: C
authors.lastname: Tanaka
mesh_terms: D015067:17-Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D043582:5-alpha-Dihydroprogesterone; D000107:Acetylation; D000818:Animals; D002855:Chromatography, Thin Layer; D005753:Gastric Mucosa / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D006168:Guinea Pigs; D008297:Male; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011277:Pregnanediones / Q000378:metabolism; D011374:Progesterone / Q000378:metabolism*; D013997:Time Factors
chemical_list: D011277:Pregnanediones; D011374:Progesterone; D043582:5-alpha-Dihydroprogesterone; D010088:Oxidoreductases; D015067:17-Hydroxysteroid Dehydrogenases; C044256:3 (or 17)-beta-hydroxysteroid dehydrogenase; C022447:3-oxo-5-alpha-steroid 4-dehydrogenase (NADP(+))