Kinetic analysis of 5 alpha-reductase isoenzymes in benign prostatic hyperplasia (BPH).
J Steroid Biochem
; 19(1A): 169-73, 1983 Jul.
Article
em En
| MEDLINE
| ID: mdl-6193340
ABSTRACT
Kinetic parameters (KM and Vmax) of the 5 alpha-reductase activities in homogenates of stroma and epithelium, isolated from BPH tissue, were determined using both testosterone and progesterone as substrate. The mean KM values for stromal 5 alpha-reductase, at 67.9 nM and 27.7 nM for testosterone and progesterone respectively, were 3-4-fold higher than the comparable KM estimates for the epithelial enzyme. The KM estimates for the epithelial 5 alpha-reductase showed little variation whereas those measured in the stromal homogenates could be subgrouped at less than 50 nM and greater than 100 nM. The mean Vmax for the stromal 5 alpha-reductase was approximately 235 pmol/30 min/mg protein irrespective of the substrate used; a value 10-fold higher than the Vmax of the epithelial 5 alpha-reductase. Preliminary experiments with inhibitors of 5 alpha-reductase demonstrated that the stromal and epithelial enzymes differed in their relative sensitivity to these compounds. Three major conclusions can be drawn from these results:
first, that progesterone is a better substrate for prostatic 5 alpha-reductase than testosterone; second, that BPH tissue has at least two isoenzymes of 5 alpha-reductase--one in the epithelium and one (or more) in the stroma; and third, in hyperplastic prostates, most of the 5 alpha-reductase molecules are located in the stroma.
Buscar no Google
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Oxirredutases
/
Próstata
/
Hiperplasia Prostática
/
3-Oxo-5-alfa-Esteroide 4-Desidrogenase
/
Isoenzimas
Limite:
Aged
/
Humans
/
Male
/
Middle aged
Idioma:
En
Revista:
J Steroid Biochem
Ano de publicação:
1983
Tipo de documento:
Article