Silva P, Ross B, Spokes K
Am J Physiol. 1980 Apr;238(4):F290-5. doi: 10.1152/ajprenal.1980.238.4.F290.
Kidneys of rats treated with methylprednisolone show altered substrate requirements for sodium reabsorption when perfused in vitro. Such kidneys synthesize glucose from lactate at twice the rate of control. Optimum sodium reabsorption is not seen with glucose, which is normally the preferred substrate. Sodium reabsorption is restored toward normal by the combination of glucose and butyrate, by pyruvate, or by 3-mercaptopicolinate. All of these results point to a metabolic adaptation in the kidney; butyrate may improve sodium reabsorption by sparing glucose, pyruvate is a gluconeogenic precursor and an effective fuel of respiration, and 3-mercaptopicolinate is an inhibitor of gluconeogenesis. In kidneys from rats treated with methylprednisolone there is an increased requirement for metabolic energy because of the increased rate of gluconeogenesis. It is suggested that the availability of energy from glucose oxidation is limited in part by the diversion of pyruvate back to glucose. Under these special circumstances, gluconeogenesis competes with sodium reabsorption in the intact kidney.
用甲基泼尼松龙治疗的大鼠肾脏在体外灌注时，对钠重吸收的底物需求发生了改变。此类肾脏从乳酸合成葡萄糖的速率是对照的两倍。通常作为首选底物的葡萄糖并不能实现最佳的钠重吸收。葡萄糖与丁酸盐联合使用、丙酮酸或3 - 巯基吡啶甲酸盐可使钠重吸收恢复正常。所有这些结果都表明肾脏存在代谢适应性；丁酸盐可能通过节省葡萄糖来改善钠重吸收，丙酮酸是糖异生的前体和有效的呼吸燃料，而3 - 巯基吡啶甲酸盐是糖异生的抑制剂。在用甲基泼尼松龙治疗的大鼠肾脏中，由于糖异生速率增加，对代谢能量的需求也增加。有人提出，葡萄糖氧化产生的能量可用性部分受到丙酮酸回流向葡萄糖的限制。在这些特殊情况下，糖异生在完整肾脏中与钠重吸收相互竞争。
