O'Rourke M F, Tuma D J, Casey C A
Department of Internal Medicine, University of Nebraska Medical Center, Omaha, U.S.A.
Biochem Pharmacol. 1997 May 15;53(10):1445-50. doi: 10.1016/s0006-2952(97)00085-3.
We have shown previously that binding and processing of epidermal growth factor are impaired in livers of ethanol-fed rats. In the current study, we examined these ethanol-induced alterations in greater detail by studying both high and low affinity epidermal growth factor binding as well as the ability of added ligand to stimulate receptor autophosphorylation. We also measured the binding of anti-receptor antibody to intact and permeabilized cells in order to determine more accurately the levels of receptor protein. Hepatocytes were isolated from ethanol-fed and pair-fed control rats. Ligand binding, antibody binding, and ligand-induced receptor autrophosphorylation were measured in the respective cell populations. In ethanol-fed animals, binding to both high and low affinity states of the hepatic epidermal growth factor receptor was decreased by 40-50% (P < 0.01). This ethanol-induced decrease in ligand binding was accompanied by a reduced ability of epidermal growth factor to stimulate receptor autophosphorylation (32% decrease, P < 0.01). In contrast, binding of anti-receptor antibody was not altered in ethanol-fed animals. In conclusion, chronic ethanol feeding decreased epidermal growth factor binding with a concomitant decrease in the ability of the receptor tyrosine kinase to phosphorylate tyrosine residues. These changes were not accompanied by an actual decrease in receptor protein content. These findings could be relevant to modified responses to this growth factor in the livers of chronic ethanol-fed animals.
我们之前已经表明，在喂食乙醇的大鼠肝脏中，表皮生长因子的结合和加工受损。在当前研究中，我们通过研究高亲和力和低亲和力表皮生长因子结合以及添加配体刺激受体自身磷酸化的能力，更详细地研究了这些乙醇诱导的改变。我们还测量了抗受体抗体与完整细胞和通透细胞的结合，以便更准确地确定受体蛋白的水平。从喂食乙醇的大鼠和配对喂食的对照大鼠中分离肝细胞。在各自的细胞群体中测量配体结合、抗体结合和配体诱导的受体自身磷酸化。在喂食乙醇的动物中，肝表皮生长因子受体高亲和力和低亲和力状态的结合均降低了40 - 50%（P < 0.01）。这种乙醇诱导的配体结合减少伴随着表皮生长因子刺激受体自身磷酸化的能力降低（降低32%，P < 0.01）。相比之下，喂食乙醇的动物中抗受体抗体的结合没有改变。总之，长期喂食乙醇会降低表皮生长因子结合，同时受体酪氨酸激酶磷酸化酪氨酸残基的能力也会降低。这些变化并没有伴随着受体蛋白含量的实际减少。这些发现可能与慢性喂食乙醇的动物肝脏中对这种生长因子的反应改变有关。
