Bickers D R, Marcelo C L, Dutta-Choudhury T, Mukhtar H
J Pharmacol Exp Ther. 1982 Oct;223(1):163-8.
Studies of drug and carcinogen metabolism in cultured keratinocytes and in intact epidermis from the skin of BALB/C mice were performed. The cultured cells were shown to retain 33 to 40% of corresponding intact epidermal aryl hydrocarbon hydroxylase (AHH), 7-ethoxycoumarin-O-de-ethylase (7-ED) and epoxide hydrolase activities. In vitro treatment of the cells or in vivo application to the skin of animals with the polycyclic aromatic hydrocarbons benz(a)anthracene (BA) or benzo(a)pyrene resulted in significant induction of AHH and 7-ED activities. The responsiveness of AHH was greater than that of 7-ED in both preparations. BA (4 x 10(-4) M) induced AHH and 7-ED at least 12- and 4-fold, respectively, in either the keratinocytes or intact epidermis, whereas epoxide hydrolase activity was not altered in either preparation. All of these enzyme activities were predominantly located in the microsomal fraction of the keratinocytes and the epidermis. Keratinocyte AHH had a pH optimum at 7.4. The apparent Km for benzo(a)pyrene as substrate in control and BA-induced cells was 10 and 6 microM, respectively, whereas Vmax was 15-fold greater in the carcinogen-treated cells. CO-difference spectra demonstrated the presence of the heme-protein cytochrome P-450 in microsomes prepared from keratinocytes and intact epidermis; absorption maximum was between 451 to 453 nm. The metabolic activity of keratinocytes was further demonstrated in the Ames mutagen assay. A supernatant (9000 x g) prepared from keratinocytes pretreated with BA enhanced the mutagenesis of 2-aminoanthracene in the TA98 strain of Salmonella typhimurium. These studies indicate that cultured keratinocytes provide a useful experimental model system for the study of epidermal drug and carcinogen metabolism.
对BALB/C小鼠皮肤的角质形成细胞和完整表皮中的药物及致癌物代谢进行了研究。结果显示，培养的细胞保留了相应完整表皮芳烃羟化酶（AHH）、7-乙氧基香豆素-O-脱乙基酶（7-ED）和环氧化物水解酶活性的33%至40%。用多环芳烃苯并(a)蒽（BA）或苯并(a)芘对细胞进行体外处理或对动物皮肤进行体内应用，可显著诱导AHH和7-ED活性。在两种制剂中，AHH的反应性均高于7-ED。BA（4×10⁻⁴M）在角质形成细胞或完整表皮中分别至少诱导AHH和7-ED 12倍和4倍，而在两种制剂中环氧化物水解酶活性均未改变。所有这些酶活性主要位于角质形成细胞和表皮的微粒体部分。角质形成细胞AHH的最适pH为7.4。在对照细胞和BA诱导的细胞中，以苯并(a)芘为底物的表观Km分别为10μM和6μM，而在致癌物处理的细胞中Vmax大15倍。一氧化碳差光谱证明从角质形成细胞和完整表皮制备的微粒体中存在血红素蛋白细胞色素P-450；最大吸收在451至453nm之间。在Ames诱变试验中进一步证明了角质形成细胞的代谢活性。用BA预处理的角质形成细胞制备的上清液（9000×g）增强了鼠伤寒沙门氏菌TA98菌株中2-氨基蒽的诱变作用。这些研究表明，培养的角质形成细胞为研究表皮药物和致癌物代谢提供了一个有用的实验模型系统。
