Yanagisawa H, Wada O
Department of Hygiene and Preventive Medicine, Faculty of Medicine, Saitama Medical School, Japan.
Nephron. 1998;78(2):179-86. doi: 10.1159/000044908.
The effects of dietary protein on the in vitro production of prostaglandin (PG) E2, 6-keto PGF1alpha, and thromboxane B2 (TxB2) were examined in cortical and medullary tubules from rats fed a low (6% casein) or a high (40% casein) protein diet for approximately 8 weeks. PGE2 was a major eicosanoid produced by rat renal tubules (PGE2 > TxB2 > 6-keto PGF1alpha). Medullary tubules produced significantly greater amounts of PGE2, 6-keto PGF1alpha, and TxB2 than cortical tubules. The activity of phospholipase (PL) A2 and PLC and the levels of cyclooxygenase (COX) were significantly greater in medullary tubules than in cortical tubules. The production of eicosanoids may be increased in medullary versus cortical tubules via the greater activity of these enzymes involved in eicosanoid formation. Although there were no substantial differences in the production of PGE2, 6-keto PGF1alpha, and TxB2 between cortical tubules from rats fed a low- or a high-protein diet, significant increases in the synthesis of the three eicosanoids were observed in medullary tubules from rats fed a high- versus a low-protein diet. The activity of membrane-bound PLA2 and PLC and the levels of COX were not also substantially different between cortical tubules from rats fed a low- or a high-protein diet. However, medullary tubules had significantly greater activity of membrane-associated PLA2 and COX in rats fed a high-protein diet than in those fed a low-protein diet. The activity of PLC was comparable in medullary tubules from rats fed a low- or a high-protein diet. We conclude that a high protein intake selectively enhances eicosanoid production in rat medullary tubules probably via activation of the PLA2-COX pathway.
研究了蛋白质饮食对喂食低蛋白（6%酪蛋白）或高蛋白（40%酪蛋白）饮食约8周的大鼠皮质和髓质肾小管中前列腺素（PG）E2、6-酮PGF1α和血栓素B2（TxB2）体外生成的影响。PGE2是大鼠肾小管产生的主要类花生酸（PGE2>TxB2>6-酮PGF1α）。髓质肾小管产生的PGE2、6-酮PGF1α和TxB2比皮质肾小管显著更多。髓质肾小管中磷脂酶（PL）A2和PLC的活性以及环氧化酶（COX）的水平比皮质肾小管显著更高。与皮质肾小管相比，髓质肾小管中类花生酸的生成可能通过参与类花生酸形成的这些酶的更高活性而增加。尽管喂食低蛋白或高蛋白饮食的大鼠皮质肾小管中PGE2、6-酮PGF1α和TxB2的生成没有实质性差异，但在喂食高蛋白与低蛋白饮食的大鼠髓质肾小管中，观察到这三种类花生酸的合成显著增加。喂食低蛋白或高蛋白饮食的大鼠皮质肾小管中膜结合PLA2和PLC的活性以及COX的水平也没有实质性差异。然而，喂食高蛋白饮食的大鼠髓质肾小管中膜相关PLA2和COX的活性比喂食低蛋白饮食的大鼠显著更高。喂食低蛋白或高蛋白饮食的大鼠髓质肾小管中PLC的活性相当。我们得出结论，高蛋白摄入可能通过激活PLA2-COX途径选择性增强大鼠髓质肾小管中类花生酸的生成。
