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J. Biol. Chem., Vol. 259, Issue 7, 4130-4135, 04, 1984
PG Quinn and AH Payne
Cultured Leydig cells exhibited time-dependent decreases in the microsomal
cytochrome P-450 enzyme activities, 17 alpha-hydroxylase and C17-20 lyase
when maintained under standard culture conditions (95% air, 5% CO2).
Inclusion of the hydroxyl radical scavenger dimethyl sulfoxide in the
culture medium, or the reduction of oxygen tension from 19 to 1% O2 was
effective in preserving these enzyme activities and the combined effects of
low O2 and dimethyl sulfoxide were synergistic. Leydig cells in culture
were treated with 1 mM 8-Br-cAMP to induce steroidogenic desensitization
which resulted in greater decreases in 17 alpha-hydroxylase and C17-20
lyase activities, as well as a diminished capacity to produce testosterone
in response to subsequent acute stimulation with 8-Br-cAMP. Reduction of
the oxygen tension from 19 to 1% O2 prevented this enhanced loss of
microsomal P- 450 activities in desensitized Leydig cells. The activity of
delta 5-3 beta-hydroxysteroid dehydrogenase-isomerase, a microsomal enzyme
which is not a P-450 enzyme, was stable in cultures of both control and
desensitized Leydig cells under all culture conditions. These data are
consistent with the hypothesis that oxygen-mediated damage is responsible
for the time-dependent decrease in 17 alpha-hydroxylase and C17-20 lyase
activities of control Leydig cells, and is the mechanism by which these
microsomal P-450 activities are further decreased in desensitized Leydig
cells. Desensitized Leydig cells exhibited a 50 and 70% decrease at 24 and
48 h, respectively, in their ability to produce testosterone in response to
subsequent acute stimulation with 8-Br- cAMP, regardless of the culture
conditions. Since desensitized Leydig cells cultured at 1% O2 showed no
greater loss of enzyme activity than did controls, loss of microsomal P-450
activities is not the cause of the diminished testosterone biosynthetic
capacity of desensitized Leydig cells.
Oxygen-mediated damage of microsomal cytochrome P-450 enzymes in cultured leydig cells. Role in steroidogenic desensitization
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