Effect of aging on kinetic parameters of 3 alpha(beta)-hydroxysteroid oxidoreductases in epithelium and stroma of human normal and hyperplastic prostate.
The accumulation of 5 alpha-dihydrotestosterone (DHT), particularly in stroma, is a possible etiological factor in regard of the age-dependent development of benign prostatic hyperplasia (BPH). In this context, we have recently demonstrated age-dependent alterations of 5 alpha-reductase, which is responsible for the irreversible conversion of testosterone to DHT. Therefore, it was also of interest to study possible age-dependent alterations of those enzymes mainly involved in the reversible metabolism of DHT to 5 alpha-androstanediols. Thus, we determined, in the presence of NADPH/NADP+, kinetic parameters [Km and maximum velocity (Vmax)] of 3-hydroxysteroid oxidoreductases (3 alpha-HSORred, 3 beta-HSORred, and 3 alpha-HSORox) in separated epithelium and stroma of 10 normal (NPR) and 20 hyperplastic prostates (BPH) and correlated the data with the age of the donors (15-86 yr). The mean Km (nanomolar concentrations +/- SEM) of 3 alpha-HSORred was significantly (P less than 0.01) higher in epithelium (NPR, 1391 +/- 181; BPH, 2150 +/- 157) than in stroma (NPR, 778 +/- 22; BPH, 749 +/- 62), indicating the presence of epithelial and stromal enzymes. The mean Km values of 3 beta-HSORred and 3 alpha-HSORox were similar. Concerning 3 alpha-HSORred, the mean potential capacity, i.e. the quotient of Vmax/Km (+/- SEM), was significantly (P less than 0.01) higher in epithelium (0.56 +/- 0.08) than in stroma (0.19 +/- 0.02) of NPR, while in BPH nearly identical mean potential capacities were found in epithelium (0.33 +/- 0.04) and stroma (0.26 +/- 0.02). The respective Vmax/Km of 3 beta-HSORred and 3 alpha-HSORox were significantly (P less than 0.05) lower. In addition, the potential capacity of all three enzymes was distinctly lower than the potential DHT-forming capacity of 5 alpha-reductase. With advancing age, the Vmax/Km decreased significantly (P less than 0.001; 3 alpha-HSORred and 3 beta-HSORred) or tendentiously (3 alpha-HSORox) in epithelium, while in stroma a significant (P less than 0.001; 3 alpha-HSORred and 3 alpha-HSORox) or tendentious (3 beta-HSORred) increase with age was found. Our results indicate that aging has a significant impact on DHT-removing enzymes. However, these enzymes counterbalance only in part the strong potential capacity of 5 alpha-reductase.
Tunn
S
S
Institute of Clinical Chemistry and Laboratory Medicine, University Clinic Bergmannsheil, Bochum, West Germany.
Haumann
R
R
Hey
J
J
Flüchter
S H
SH
Krieg
M
M
D015096:3-Hydroxysteroid Dehydrogenases / Q000378:metabolism*; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000378:metabolism*; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004848:Epithelium / Q000201:enzymology; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D011467:Prostate / Q000201:enzymology*; D011470:Prostatic Hyperplasia / Q000201:enzymology*
D009243:NAD; D009249:NADP; D015096:3-Hydroxysteroid Dehydrogenases; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase