Hernandez M L, Martinez M J, Ochoa B
Department of Physiology, University of the Basque Country Medical School, Bilbao, Spain.
Biochimie. 1996;78(1):26-32. doi: 10.1016/0300-9084(96)81325-3.
In the present study we have analysed the potential relationship between the cellular level of adenine nucleotides and the activity of microsomal cholesterol ester hydrolase by treating rat hepatocyte suspensions with fructose or adenosine. Fructose raised the microsomal hydrolysis of cholesteryl esters as a function of the dose. This ketose led to marked decreases in the cell level of ADP, ATP and total adenine nucleotide whereas that of AMP increased slightly, thus giving a rise in the cellular AMP/ATP ratio. The effects remained virtually constant over a period of 60 min. Incubation of hepatocytes in a Ca(2+)-free medium with or without ethylene glycol-bis(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid blocked by 40% the fructose-induced activation of cholesterol esterase whereas the rise in AMP/ATP was unaffected. Adenosine caused dose-dependent activations of cholesterol ester hydrolase and raised AMP, ADP and ATP concentrations as well as the AMP/ATP ratio. 2-Chloro-adenosine and N6-[L-2-phenyl-isopropyl] adenosine, non-metabolizable analogues of adenosine, did not mimic the effects of the nucleoside. A positive linear correlation exists between the percentage rises in the activity of microsomal cholesterol ester hydrolase and those in the intracellular AMP/ATP ratio in fructose- or adenosine-treated cells. These results indicate that, in microsomes from intact hepatocytes, the breakdown of cholesteryl esters to yield cholesterol and fatty acids is stimulated by fructose and adenosine and this can be explained in part by the increase in the cellular AMP/ATP ratio. In the case of fructose, also a Ca(2+)-dependent mechanism is involved.
在本研究中，我们通过用果糖或腺苷处理大鼠肝细胞悬液，分析了腺嘌呤核苷酸的细胞水平与微粒体胆固醇酯水解酶活性之间的潜在关系。果糖可使胆固醇酯的微粒体水解随剂量增加而升高。这种酮糖导致细胞内二磷酸腺苷（ADP）、三磷酸腺苷（ATP）和总腺嘌呤核苷酸水平显著降低，而一磷酸腺苷（AMP）水平略有升高，从而使细胞内AMP/ATP比值升高。在60分钟内，这些效应基本保持不变。在无钙培养基中培养肝细胞，无论有无乙二醇双（β-氨基乙醚）N,N,N',N'-四乙酸，果糖诱导的胆固醇酯酶激活均被阻断40%，而AMP/ATP的升高不受影响。腺苷引起胆固醇酯水解酶的剂量依赖性激活，并提高了AMP、ADP和ATP浓度以及AMP/ATP比值。2-氯腺苷和N6-[L-2-苯基-异丙基]腺苷，腺苷的不可代谢类似物，没有模拟核苷的作用。在果糖或腺苷处理的细胞中，微粒体胆固醇酯水解酶活性的升高百分比与细胞内AMP/ATP比值的升高百分比之间存在正线性相关。这些结果表明，在完整肝细胞的微粒体中，果糖和腺苷可刺激胆固醇酯分解产生胆固醇和脂肪酸，这部分可以用细胞内AMP/ATP比值的升高来解释。就果糖而言，还涉及一种钙依赖性机制。
