Steroid 5-alpha reductase type 2 activity in biopsies from malignant and normal prostatic tissues.
BACKGROUND
The conversion of testosterone (T) to the more potent metabolite dihydrotestosterone (DHT) by prostate-specific steroid 5 alpha-reductase isoenzymes is a key mechanism in the action of androgens in the prostate and it is important in the promotion and progression of prostate diseases. We described an adaptation of a sensitive method for evaluation of the 5 alpha-reductase type 2 (5 alpha-R2) activity using a small quantity of protein.


METHODS
We used 29 human prostate transrectal ultrasound-guided core biopsies obtained from patients (median age 70, range 55-86 y) undergoing this procedure for diagnostic purposes. 4-[(14)C]testosterone and NADPH were incubated with biopsy homogenate. Reaction products were extracted, separated by thin layer chromatography and revealed by autoradiography. Areas correspondent to T and DHT were scraped into vials and their radioactivity determined.


RESULTS
The 5 alpha-R2 activity was expressed as ln (natural logarithm). The assay was validated according to the protein concentration and incubation time linearities. The 5 alpha-R2 activity showed a significant difference between normal and neoplastic tissues with significance level set at P<0.05, mainly in the left prostate lobe. This was independent from the PSA levels.


CONCLUSIONS
Determination of 5 alpha-R2 activity, using the conditions reported herein, could be utilized as an efficient biochemical parameter of prostate neoplastic processes.
Oliveira
Osmar Luiz Magalhães
OL
Urology Service, Hospital de Clínicas de Porto Alegre, Rua Ramiro Barcelos 2350, Porto Alegre, RS, Brazil. ooliveira@hcpa.ufrgs.br
Koff
Walter José
WJ
Muraro
Francine
F
Santos
Emanuel Burck
EB
Gomes Soares
Daniel Freitas
DF
Trindade
Vera Maria Treis
VM
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000378:metabolism*; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D013196:Dihydrotestosterone / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000201:enzymology*; D011470:Prostatic Hyperplasia / Q000201:enzymology*; D011471:Prostatic Neoplasms / Q000201:enzymology*; D013739:Testosterone / Q000378:metabolism*
D013196:Dihydrotestosterone; D013739:Testosterone; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase