| RESEARCH PAPER
|Year : 1998 | Volume
| Issue : 4 | Page : 257-262
A convenient and rapid method to study enzymatic kinetics of steroid 5a-reductase inhibitors
zu-Yue Sun, Wei-Jun Zheng, Jie Feng, Zeng-Hong Tu
0bjective:To demonstrate that the inhibition of steroid 5(-reductase inhibitor could be conveniently and rapidly determined with common ultraviolet spectrophotometer.
Methods: A biochemical method to determine the activity of steroid 5(-reductase was used to evaluate the inhibition of epristeride and ffnasteride to the enzyme. The OD value of each sample was measured continuously with ultraviolet spectrophotometer. for the reason that the substrate (NADPH) has a specific absorbent wave at 340 nm. The descending curve of OD value in each tube was described from the beginning to the tenth minute, by which the descending rate of each curve could be obtained through linear regression. The initial reaction rate, the slope of descending curve, resulted from difference between initial rate of each concentration and 0 concentration (blank control) of testosterone. It implicated the activity of the 5(-reductase. In order to prove this method feasible and the inhibition of the inhibitors reliable, an in vivo test was carried out. Twenty old-aged male mongrel dogs, with over 18 cm3 volume prostates though ultrasonic examination, were chosen in vivo experiment.
Results: The inhibition constant of epristerlde (K,=25.1(1.2 nM) could be obtained according to the Lineweaver-Burk plots. Epristeride decreased the DHT concentration of serum and prostates.
Conclusion: This method is convenient, rapid and effective for studying enzymatic kinetics of steroid 5(-reductase inhibitors
Source of Support: None, Conflict of Interest: None