Goldstein R S, Contardi L R, Pasino D A, Hook J B
Toxicol Appl Pharmacol. 1987 Feb;87(2):297-305. doi: 10.1016/0041-008x(87)90291-2.
Incubation of renal cortical slices with cephaloridine (CPH) markedly inhibits pyruvate-supported gluconeogenesis, an effect which is independent of CPH-induced lipid peroxidation. CPH was found to inhibit pyruvate-supported gluconeogenesis in a time-and concentration-dependent manner. Pyruvate-supported gluconeogenesis was inhibited as early as 10 min following incubation of renal cortical slices with 5 mM CPH. Similarly, endogenous gluconeogenesis was impaired following CPH treatment. CPH depressed the renal cortical slice content of ATP by 50%, but only following 90 and 120 min of drug exposure, suggesting that mitochondrial dysfunction does not mediate the inhibition of gluconeogenesis by CPH. To identify the intracellular site(s) of CPH inhibition of gluconeogenesis, the effects of CPH on glucose production were evaluated using substrates catalyzed by rate-limiting reactions. CPH inhibited renal cortical slice gluconeogenesis when the following substrates were used: pyruvate (mitochondrial), oxaloacetate and fructose-1,6-diphosphate (FDP) (postmitochondrial), and glucose-6-phosphate (G6P, endoplasmic reticulum). Inhibition of G6P-supported gluconeogenesis occurred within 5 min of incubation with 5 mM CPH. Direct addition of CPH to microsomal suspensions inhibited G6Pase activity in a concentration-dependent fashion. By contrast, addition of CPH to cytosolic fractions did not affect FDPase activity. CPH increased the Km and decreased the Vmax of G6Pase, indicating mixed competitive and noncompetitive inhibition. These data indicate that the profound inhibition of renal cortical slice gluconeogenesis by CPH is mediated by inhibition of microsomal G6Pase activity.
肾皮质切片与头孢菌素（CPH）一起孵育可显著抑制丙酮酸支持的糖异生，这一效应与CPH诱导的脂质过氧化无关。发现CPH以时间和浓度依赖性方式抑制丙酮酸支持的糖异生。肾皮质切片与5 mM CPH孵育后10分钟，丙酮酸支持的糖异生就受到抑制。同样，CPH处理后内源性糖异生也受损。CPH使肾皮质切片中的ATP含量降低50%，但仅在药物暴露90分钟和120分钟后出现这种情况，这表明线粒体功能障碍并非CPH抑制糖异生的介导因素。为了确定CPH抑制糖异生的细胞内位点，使用限速反应催化的底物评估了CPH对葡萄糖生成的影响。当使用以下底物时，CPH抑制肾皮质切片的糖异生：丙酮酸（线粒体）、草酰乙酸和果糖-1,6-二磷酸（FDP，线粒体后）以及葡萄糖-6-磷酸（G6P，内质网）。与5 mM CPH孵育5分钟内，G6P支持的糖异生就受到抑制。将CPH直接添加到微粒体悬浮液中以浓度依赖性方式抑制G6P酶活性。相比之下，将CPH添加到胞质组分中并不影响FDP酶活性。CPH增加了G6P酶的Km并降低了其Vmax，表明存在混合竞争性和非竞争性抑制。这些数据表明，CPH对肾皮质切片糖异生的深度抑制是通过抑制微粒体G6P酶活性介导的。
