Gerbracht U, Einig C, Oesterle D, Deml E, Schlatterer B, Eigenbrodt E
Institute of Veterinary Biochemistry, University of Geissen, FRG.
Carcinogenesis. 1990 Dec;11(12):2111-5. doi: 10.1093/carcin/11.12.2111.
The effect of di(2-ethylhexyl)phthalate (DEHP) on diethylnitrosamine (DEN)-initiated preneoplastic liver lesions with expression of gamma-glutamyltranspeptidase (GGTase) and loss of adenosine triphosphatase (ATPase) as well as alterations of hepatic carbohydrate metabolism in male and female Sprague-Dawley rats have been investigated. Two treatment schedules have been compared with respect to their sensitivity by the histochemical demonstration of preneoplastic islands and by the biochemical determination of alterations in enzyme activities of liver homogenates and of serum, the last indicating hepatotoxicity. For initiation, a single dose of DEN was given, followed by treatment with various doses of DEHP given three times weekly by gavage for 7 or 11 consecutive weeks. As histochemical enzyme markers, the expression of positive GGTase as well as the deficiency in ATPase were used for identification of liver foci. The weanling female rats (protocol A) were found to be more sensitive to the carcinogenic effect of DEN in view of foci incidence than the mature male rats which underwent partial hepatectomy prior to DEN application. The administration of 200 mg DEHP/kg body wt increased the incidence of ATPase-deficient foci in both male and female rats; however, concentrations of 1000 and 2000 mg DEHP/kg decreased the incidence of liver foci. The number of foci with expression of GGTase was only slightly increased in female rats following a DEHP concentration of 50 mg/kg, and 200 mg/kg body wt. DEHP alone did not induce preneoplastic lesions that could be identified by these two markers. Biochemical investigations indicate that DEHP alters the metabolic pattern in liver. An increase of the NADP-linked enzymes glucose-6-phosphate dehydrogenase (G6PDH), malic enzyme, extra-mitochondrial ICDH as well as an enhancement of NAD-dependent alpha-G3PDH and lactate dehydrogenase were found following DEHP administration. On the other hand the glycolytic enzymes pyruvate kinase (PK) and enolase as well as the gluconeogenetic enzyme fructose-1,6-bisphosphatase (FBPase) were significantly reduced. In protocol B (male rats) the reactions of PK, FBPase and malic enzyme were more altered after DEHP exposure than in protocol A, while the activity of G6PDH was more increased in protocol A. Most enzymes being involved in the carbohydrate metabolism are influenced by DEHP in a dose-dependent manner. There was no increase in serum FBPase activity in both male and female rats after DEHP treatment but a reduction of glutamate-oxalate-transaminase and glutamate-pyruvate-transaminase activities was observed.(ABSTRACT TRUNCATED AT 400 WORDS)
研究了邻苯二甲酸二（2-乙基己基）酯（DEHP）对二乙基亚硝胺（DEN）引发的、具有γ-谷氨酰转肽酶（GGTase）表达和三磷酸腺苷酶（ATPase）缺失的癌前肝损伤以及对雄性和雌性斯普拉格-道利大鼠肝脏碳水化合物代谢改变的影响。通过癌前岛的组织化学显示以及肝脏匀浆和血清酶活性改变的生化测定，比较了两种治疗方案的敏感性，后者表明肝毒性。起始时给予单次剂量的DEN，随后用不同剂量的DEHP每周经口灌胃三次，连续7或11周。作为组织化学酶标记物，阳性GGTase的表达以及ATPase的缺乏用于鉴定肝灶。断奶雌性大鼠（方案A）在灶发生率方面对DEN的致癌作用比在给予DEN之前接受部分肝切除术的成熟雄性大鼠更敏感。给予200 mg DEHP/kg体重增加了雄性和雌性大鼠中ATPase缺乏灶的发生率；然而，1000和2000 mg DEHP/kg的浓度降低了肝灶的发生率。在DEHP浓度为50 mg/kg和200 mg/kg体重后，雌性大鼠中表达GGTase的灶数量仅略有增加。单独的DEHP不会诱导可通过这两种标记物鉴定的癌前病变。生化研究表明，DEHP改变了肝脏的代谢模式。给予DEHP后发现与NADP相关的酶葡萄糖-6-磷酸脱氢酶（G6PDH）、苹果酸酶、线粒体外异柠檬酸脱氢酶增加，以及NAD依赖的α-甘油磷酸脱氢酶和乳酸脱氢酶增强。另一方面，糖酵解酶丙酮酸激酶（PK）和烯醇化酶以及糖异生酶果糖-1,6-二磷酸酶（FBPase）显著降低。在方案B（雄性大鼠）中，DEHP暴露后PK、FBPase和苹果酸酶的反应比方案A中变化更大，而方案A中G6PDH的活性增加更多。大多数参与碳水化合物代谢的酶受到DEHP的剂量依赖性影响。DEHP处理后雄性和雌性大鼠血清FBPase活性均未增加，但观察到谷氨酸草酰乙酸转氨酶和谷氨酸丙酮酸转氨酶活性降低。（摘要截断于400字）
