Zhao W, Ramos K S
Department of Physiology and Pharmacology, College of Veterinary Medicine, Texas A & M University, College Station 77843-4466, USA.
Toxicology. 1995 May 23;99(3):179-89. doi: 10.1016/0300-483x(94)03028-z.
Studies were conducted to examine the effects of benzo[a]pyrene (BaP) and related-aromatic hydrocarbons (AHs) on the DNA synthetic profiles of adult rat hepatocytes in primary culture. Scheduled DNA synthesis in control cultures peaked at 64 h and was negligible by 72 h after initial seeding of freshly isolated hepatocytes. A concentration-dependent inhibition of DNA synthesis was observed in 1-day old hepatocyte cultures treated with BaP (0.3-30 microM) for up to 28 h. Comparable inhibitory responses were observed in cultures treated for 24 h with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, 0.01-1 nM) or 2,3,7,8-tetrachlorodibenzofuran (TCDF, 0.01-1 nM), but not in cultures treated with perylene (0.01-100 nM) or benzo[e])pyrene (1-1000 nM). Ethoxyresorufin-O-deethylase (EROD) activity was highly inducible in hepatocytes challenged for 24 h with BaP (0.3-3 microM) or TCDD (0.1-100 nM) with peak induction observed at 12 or 36 h after chemical challenge, respectively. To determine if DNA synthesis inhibition by these agents involved aryl hydrocarbon receptor (AhR)-related events, subsequent experiments were conducted to examine the interactions of alpha-naphthoflavone (alpha-NF) and ellipticine (ET) with BaP and TCDD in this cell system. Pretreatment with alpha-NF (10 nM) for 24 h prevented the inhibitory effects of both BaP (3 microM) and TCDD (1 nM), while ET (0.01 nM) pretreatment selectively antagonized the effects of BaP (3 microM). Pretreatment of hepatocytes with TCDD or TCDF (1 nM) for 24 h before the onset of DNA synthesis followed by challenge with BaP (3 microM) partially antagonized the inhibitory response to BaP. These data implicate AhR-related signal transduction in the inhibition of hepatocyte DNA synthesis by BaP and related AHs and suggest that in the case of BaP, metabolism by cytochrome P450 to toxic intermediates contributes to the inhibitory response.
开展了多项研究，以考察苯并[a]芘（BaP）及相关芳烃（AHs）对原代培养成年大鼠肝细胞DNA合成谱的影响。对照培养物中的定时DNA合成在64小时达到峰值，在新鲜分离的肝细胞初次接种后72小时可忽略不计。在用BaP（0.3 - 30微摩尔）处理长达28小时的1日龄肝细胞培养物中，观察到DNA合成受到浓度依赖性抑制。在用2,3,7,8 - 四氯二苯并 - p - 二恶英（TCDD，0.01 - 1纳摩尔）或2,3,7,8 - 四氯二苯并呋喃（TCDF，0.01 - 1纳摩尔）处理24小时的培养物中，观察到了类似的抑制反应，但在用苝（0.01 - 100纳摩尔）或苯并[e]芘（1 - 1000纳摩尔）处理的培养物中未观察到。在用BaP（0.3 - 3微摩尔）或TCDD（0.1 - 100纳摩尔）攻击24小时的肝细胞中，乙氧基异吩恶唑酮 - O - 脱乙基酶（EROD）活性高度可诱导，分别在化学攻击后12或36小时观察到诱导峰值。为了确定这些试剂对DNA合成的抑制是否涉及芳烃受体（AhR）相关事件，随后开展了实验，以考察α - 萘黄酮（α - NF）和玫瑰树碱（ET）与BaP和TCDD在该细胞系统中的相互作用。用α - NF（10纳摩尔）预处理24小时可防止BaP（3微摩尔）和TCDD（1纳摩尔）的抑制作用，而ET（0.01纳摩尔）预处理则选择性地拮抗BaP（3微摩尔）的作用。在DNA合成开始前用TCDD或TCDF（1纳摩尔）预处理肝细胞24小时，然后用BaP（3微摩尔）攻击，可部分拮抗对BaP的抑制反应。这些数据表明，AhR相关信号转导参与了BaP及相关AHs对肝细胞DNA合成的抑制，并且表明就BaP而言，细胞色素P450代谢为有毒中间体有助于产生抑制反应。
