Kline E L, Carland K C, Warren J T, Smith T J
Department of Microbiology, Clemson University, South Carolina 29634-1909.
Cancer Res. 1988 Jul 1;48(13):3586-90.
To assess the effect of androgens on tyrosinase activity in B16/C3 melanoma cell cultures, proliferating cultures were treated with testosterone (50 nM) or one of several other androgenic analogues and metabolites. None of these compounds influenced basal enzyme activity. Imidazole (10 mM), however, is a potent inducer of tyrosinase in this cell line. Testosterone blocked induction of tyrosinase by imidazole almost completely. This effect was dose dependent, being maximal at 10 nM and half-maximal at approximately 3 nM, and was rapid, occurring within 15 min. When cultures treated with both imidazole and testosterone were shifted to medium containing only imidazole, enzyme activity approximated that seen in cultures never receiving testosterone within 10 h of the shift. The other steroids tested failed to influence imidazole induction of the enzyme. This action of testosterone could not be demonstrated in broken cell preparations. Results of studies involving inhibitors of protein and RNA synthesis, as well as those quantitating mRNA hybridizable to a synthesized 20-base pair deoxyoligonucleotide tyrosinase probe, suggest that testosterone is blocking imidazole induction at a pretranslational level.
为评估雄激素对B16/C3黑色素瘤细胞培养物中酪氨酸酶活性的影响，用睾酮（50 nM）或其他几种雄激素类似物及代谢产物之一处理增殖培养物。这些化合物均未影响基础酶活性。然而，咪唑（10 mM）是该细胞系中酪氨酸酶的有效诱导剂。睾酮几乎完全阻断了咪唑对酪氨酸酶的诱导作用。这种作用呈剂量依赖性，在10 nM时最大，在约3 nM时为半数最大效应，且迅速，在15分钟内即可出现。当用咪唑和睾酮处理的培养物转移至仅含咪唑的培养基中时，在转移后10小时内，酶活性接近从未接受过睾酮处理的培养物中的酶活性。所测试的其他类固醇未能影响咪唑对该酶的诱导作用。在破碎细胞制剂中未证实睾酮的这种作用。涉及蛋白质和RNA合成抑制剂的研究结果，以及对可与合成的20碱基对脱氧寡核苷酸酪氨酸酶探针杂交的mRNA进行定量的研究结果表明，睾酮在翻译前水平阻断了咪唑的诱导作用。
