Zeillinger R, Spona J
Endocrinol Exp. 1984 Sep;18(3):141-50.
The effect of norethisterone, norethisterone acetate, ethinylestradiol and of a cyanoketone on the activity of HSD have been studied. Rat Leydig cells and extracts of Pseudomonas testosteroni were used as enzyme sources. Conversion of [3H]DHEA to A and [3H]pregnenolone to progesterone were used for the assay of enzyme activity. Km values for each substrate for Leydig cells and for bacterial enzyme were: 1.5 x 10(-5) mol l-1 and 6.0 x 10(-5) mol l-1 DHEA; 1.3 x 10(-5) mol and 7.7 x 10(-5) mol l-1 pregnenolone. For investigation of inhibition [3H]DHEA was used as substrate and apparent Ki values were calculated by Dixon plot analysis. In both systems norethisterone showed no inhibition of the enzyme. Norethisterone acetate proved also to be not inhibitory; only residual affinity to the enzyme was noted (Ki = 8.0 x 10(-5) mol l-1: Leydig cell preparation; Ki = 9.4 x 10(-5) mol l-1: bacterial enzyme). Different result sin the two systems were obtained for ethinylestradiol and for a combination with norethisterone acetate. Ethinylestradiol or the combination with the progestin (Ki = 0.5 x 10(-5) mol; 1.4 x 10(-5) mol l-1) showed noteworthy inhibition of the bacterial enzyme but only weak competition for binding to the active site of the enzyme in rat Leydig cells (Ki = 6.0 x 10(-5) mol l-1; 8.3 x 10(-5) mol l-1). It is concluded that there are greater differences between the two enzymes than considered previously. As expected, cyanoketone proved to be the most effective inhibitor in both systems. The most important result seems to be, that norethisterone does not inhibit HSD. This suggests that there is no causal relationship between hypospadias and progestins administered to females during pregnancy.
已研究了炔诺酮、醋酸炔诺酮、炔雌醇及一种氰基酮对羟类固醇脱氢酶（HSD）活性的影响。大鼠睾丸间质细胞和睾丸酮假单胞菌提取物用作酶源。用[3H]脱氢表雄酮（DHEA）转化为雄烯二酮（A）以及[3H]孕烯醇酮转化为孕酮来测定酶活性。睾丸间质细胞和细菌酶对每种底物的米氏常数（Km值）分别为：DHEA为1.5×10⁻⁵mol/L和6.0×10⁻⁵mol/L；孕烯醇酮为1.3×10⁻⁵mol和7.7×10⁻⁵mol/L。为研究抑制作用，以[3H]DHEA作为底物，并通过Dixon作图分析计算表观抑制常数（Ki值）。在两个系统中，炔诺酮均未显示出对该酶的抑制作用。醋酸炔诺酮也被证明无抑制作用；仅观察到其与酶有残余亲和力（Ki = 8.0×10⁻⁵mol/L：睾丸间质细胞制剂；Ki = 9.4×10⁻⁵mol/L：细菌酶）。炔雌醇以及与醋酸炔诺酮的组合在两个系统中得到了不同结果。炔雌醇或与孕激素的组合（Ki = 0.5×10⁻⁵mol；1.4×10⁻⁵mol/L）对细菌酶显示出显著抑制作用，但在大鼠睾丸间质细胞中对酶活性位点的结合仅表现出弱竞争（Ki = 6.0×10⁻⁵mol/L；8.3×10⁻⁵mol/L）。得出的结论是，这两种酶之间的差异比之前认为的更大。正如预期的那样，氰基酮在两个系统中均被证明是最有效的抑制剂。最重要的结果似乎是，炔诺酮不抑制HSD。这表明尿道下裂与孕期给予女性的孕激素之间不存在因果关系。
