Bánhegyi G, Mandl J, Antoni F, Garzó T
Biochim Biophys Acta. 1987 Mar 11;927(3):406-16. doi: 10.1016/0167-4889(87)90106-6.
Aminopyrine oxidation was studied in isolated hepatocytes prepared from 24-h-starved mice (i) after induction of the NADPH-generating malic enzyme and glucose-6-phosphate dehydrogenase, but not the mixed function oxygenases by fructose, (ii) after induction of both mixed function oxygenases and NADPH-generating malic enzyme and glucose-6-phosphate dehydrogenase by phenobarbital and (iii) without any pretreatment. Phenobarbital pretreatment, as expected, increased the rate of aminopyrine oxidation of isolated hepatocytes. However, fructose pretreatment also enhanced the rate of N-demethylation of aminopyrine by more than 100% supporting the view that the availability of NADPH is rate limiting in drug oxidation under certain conditions. The role of malic enzyme and glucose-6-phosphate dehydrogenase in the NADPH supply for aminopyrine oxidation was investigated by the addition of two groups of gluconeogenic precursors: lactate or alanine and glycerol or fructose with the simultaneous measurement of glucose synthesis and aminopyrine N-demethylation. There was a clear correlation between the increased rate of aminopyrine oxidation and the decreases of glucose production caused by aminopyrine. Gluconeogenesis in the presence of 1 mM aminopyrine was decreased by 70-80% when alanine or lactate were used as precursors, it was decreased by only 35-40% when glucose production was started from glycerol or fructose; in an accordance with the facts that NADPH generation and gluconeogenesis starting from alanine or lactate share two common intermediates--malate and glucose-6 phosphate--, while there is only one common intermediate--glucose-6 phosphate--if fructose or glycerol are used. Similar results were obtained with the addition of the structurally dissimilar hexobarbital. It is concluded that besides malic enzyme, glucose-6-phosphate dehydrogenase also takes part in NADPH supply for drug oxidation in glycogen-depleted hepatocytes.
在从饥饿24小时的小鼠制备的分离肝细胞中研究了氨基比林氧化：(i) 在用果糖诱导产生NADPH的苹果酸酶和葡萄糖-6-磷酸脱氢酶后，但未诱导混合功能氧化酶；(ii) 在用苯巴比妥诱导混合功能氧化酶以及产生NADPH的苹果酸酶和葡萄糖-6-磷酸脱氢酶后；(iii) 未经任何预处理。正如预期的那样，苯巴比妥预处理提高了分离肝细胞中氨基比林的氧化速率。然而，果糖预处理也使氨基比林的N-去甲基化速率提高了100%以上，这支持了在某些条件下NADPH的可用性是药物氧化的限速因素这一观点。通过添加两组糖异生前体：乳酸或丙氨酸以及甘油或果糖，并同时测量葡萄糖合成和氨基比林N-去甲基化，研究了苹果酸酶和葡萄糖-6-磷酸脱氢酶在氨基比林氧化的NADPH供应中的作用。氨基比林氧化速率的增加与氨基比林引起的葡萄糖生成减少之间存在明显的相关性。当使用丙氨酸或乳酸作为前体时，在1 mM氨基比林存在下糖异生减少了70 - 80%，而当从甘油或果糖开始葡萄糖生成时，糖异生仅减少了35 - 40%；这与以下事实一致，即从丙氨酸或乳酸开始的NADPH生成和糖异生共享两个共同中间体——苹果酸和葡萄糖-6-磷酸，而如果使用果糖或甘油则只有一个共同中间体——葡萄糖-6-磷酸。添加结构不同的己巴比妥也得到了类似的结果。得出的结论是，除了苹果酸酶外，葡萄糖-6-磷酸脱氢酶也参与糖原耗尽的肝细胞中药物氧化的NADPH供应。
