Purification and properties of 3 alpha-hydroxysteroid dehydrogenase from rat brain cytosol. Inhibition by nonsteroidal anti-inflammatory drugs and progestins.
The 3 alpha-hydroxysteroid dehydrogenase (EC 1.1.1.50) of rat brain cytosol has been purified to apparent homogeneity. The purification procedure involves six successive steps, includes one affinity chromatography, and yields enzyme which displays a 1,550-fold enhancement in specific activity. The homogeneous enzyme has a Km of 8.0 microM for 5 alpha-dihydrotestosterone, a Vmax of 1.3 mumol of 3 alpha-androstanediol formed per h/mg of protein, and displays a preference for NADPH. It appears to be the major activity responsible for the reduction of 5 alpha-dihydrotestosterone in this tissue and may play a pivotal role in brain androgen metabolism. The homogeneous enzyme has several properties in common with the 3 alpha-hydroxysteroid dehydrogenase purified from rat liver cytosol (Penning, T. M., Mukharji, I., Barrows, S., and Talalay, P. (1984) Biochem. J. 222, 601-611). It is a monomer with a molecular weight of 31,000, it has a pI of 5.5, and it is potently inhibited by the nonsteroidal anti-inflammatory drugs (IC50 value for indomethacin = 2.0 microM). The potency of inhibition observed for the brain enzyme parallels that observed for cyclooxygenase: indomethacin greater than fenamates greater than l-methylpyrrole acetic acids greater than arylpropionic acids greater than salicylates greater than acetaminophen. Examination of a variety of steroidal contraceptives as modulators of the dehydrogenase indicates that ethinylestradiol is a very poor inhibitor (IC50 = 100 microM), while 6-medroxyprogesterone acetate (Provera) is an extremely potent inhibitor (IC50 = 0.2 microM). The possibility exists that brain androgen metabolism may be altered by the nonsteroidal anti-inflammatory drugs and synthetic progestins.
Penning
T M
TM
Sharp
R B
RB
Krieger
N R
NR
D015096:3-Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors / Q000302:isolation & purification*; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D001921:Brain / Q000166:cytology / Q000201:enzymology*; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D003600:Cytosol / Q000201:enzymology; D013196:Dihydrotestosterone / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D007213:Indomethacin / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008525:Medroxyprogesterone / Q000031:analogs & derivatives / Q000494:pharmacology; D017258:Medroxyprogesterone Acetate; D011372:Progestins / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D000893:Anti-Inflammatory Agents; D011372:Progestins; D013196:Dihydrotestosterone; D017258:Medroxyprogesterone Acetate; D015096:3-Hydroxysteroid Dehydrogenases; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); D008525:Medroxyprogesterone; D007213:Indomethacin