Uptake and metabolism of androgen by the human epididymis in vitro

M. A. de Larminat, M. J. Hinrichsen, C. Scorticati, J. M. Ghirlanda, J. A. Blaquier, R. S. Calandra
1980 Reproduction  
Uptake and metabolism of [3H]testosterone, mainly to 5\g=a\-dihydrotestosterone (5\g=a\-DHT) and 5\g=a\-androstanediolwere higher in the caput than in the cauda epididymidis in vitro. The metabolites represented 57, 49 and 47% of the total radioactivity in the caput, corpus and cauda epididymidis, respectively; subcellular distributions of the metabolites in each segment showed 67% of total radioactivity in cytosol and 18% in the nuclei. In both fractions, the amount of 5\g=a\-DHTwas greater
more » ... n that of androstanediol while the reverse was true for the mitochondria and microsomes. The distribution of 5\g=a\-reductaseactivity in subcellular fractions was similar to that of the microsomal marker enzyme NADPH: cytochrome C reductase, whilst 3 \ g = a \ -h y d r o x y s t e r o i d dehydrogenase was found mainly in the cytosol. Maximal 5\g=a\-reductaseactivity was at pH 5\m=.\3,apparent Km values in the microsomal and nuclear fractions were 1\m=.\65 \ m=+-\0\m=.\7and 1\m=.\75\ m=+-\0\m=.\36\m=x\ 10\m=-\6 M respectively, and the Vmax in these preparations was 5\m=.\28\ m=+-\1\m=.\19 and 3\m=.\1\ m=+-\ 0\m=.\52pmol/mg protein/min, respectively. The activity of 5\g=a\-reductase was inhibited by Zn2+, Cu2+, Ba2+ and Cd2+ and by epitestosterone, progesterone and 4-androstene-3-one-17\g=b\-carboxylic acid.
doi:10.1530/jrf.0.0590397 pmid:7431296 fatcat:37krn3yvh5efzmru2fqnmtpid4