Han H J, Choi H J, Park S H
Department of Veterinary Physiology, College of Veterinary Medicine, Hormone Research Center, Chonnam National University, Kwangju, Korea.
J Cell Physiol. 2000 Jun;183(3):355-63. doi: 10.1002/(SICI)1097-4652(200006)183:3<355::AID-JCP8>3.0.CO;2-Y.
Abnormal glucose handling in the proximal tubule may play an important role in the development of diabetic nephropathy. Thus, the present study was designed to examine the effect of high glucose on alpha-methyl-D-glucopyranoside (alpha-MG) uptake and its signaling pathways in the primary cultured rabbit renal proximal tubule cells (PTCs). When PTCs were preincubated with 25 or 50 mM glucose for 4 h, 25 or 50 mM glucose significantly inhibited alpha-MG uptake, while 25 or 50 mM mannitol and L-glucose did not affect. Actinomycin D and cycloheximide did not block the effect of high glucose on alpha-MG uptake. Twenty-five millimoles glucose-induced inhibition of alpha-MG uptake was blocked by mepacrine and AACOCF(3), phospholipase A(2) (PLA(2)) inhibitors. Twenty-five millimoles of glucose, not mannitol or L-glucose, significantly increased the [(3)H]-arachidonic acid (AA) release compared to control. In addition, the 25 mM glucose-induced [(3)H]-AA release was completely blocked by mepacrine or AACOCF(3). Indomethacin, a cyclooxygenase inhibitor, blocked the high glucose-induced inhibition of alpha-MG uptake, although econazole, cytochrome P-450 a epoxygenase inhibitor, and nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, did not. On the other hand, staurosporine and bisindolylmaleimide I, protein kinase C (PKC) inhibitors, blocked 25 mM glucose-induced increase of [(3)H]-AA release and inhibition of alpha-MG uptake. However, neomycin, U 73122, and phospholipase c(PLC) inhibitors did not block the effect of 25 mM glucose on [(3)H]-AA release and alpha-MG uptake. Pretreatment of methoxyverapamil, an L-type Ca(2+) channel blocker, abolished 25 mM glucose-induced increase of [(3)H]-AA release. Indeed, 25 mM glucose increased translocation of cPLA(2) from cytosolic fraction to membrane fraction. In conclusion, the present results demonstrate that high glucose inhibits alpha-MG uptake by the increase of AA release via the activation of PKC.
近端小管中异常的葡萄糖处理可能在糖尿病肾病的发展中起重要作用。因此，本研究旨在检测高糖对原代培养的兔肾近端小管细胞（PTCs）中α-甲基-D-吡喃葡萄糖苷（α-MG）摄取及其信号通路的影响。当PTCs用25或50 mM葡萄糖预孵育4小时时，25或50 mM葡萄糖显著抑制α-MG摄取，而25或50 mM甘露醇和L-葡萄糖则无影响。放线菌素D和放线菌酮不阻断高糖对α-MG摄取的影响。25 mM葡萄糖诱导的α-MG摄取抑制被米帕林和AACOCF(3)（磷脂酶A(2)（PLA(2)）抑制剂）阻断。与对照组相比，25 mM葡萄糖而非甘露醇或L-葡萄糖显著增加了[(3)H]-花生四烯酸（AA）释放。此外，25 mM葡萄糖诱导的[(3)H]-AA释放被米帕林或AACOCF(3)完全阻断。环氧化酶抑制剂吲哚美辛阻断了高糖诱导的α-MG摄取抑制，而细胞色素P-450α环氧化酶抑制剂益康唑和脂氧合酶抑制剂去甲二氢愈创木酸（NDGA）则无此作用。另一方面，蛋白激酶C（PKC）抑制剂星形孢菌素和双吲哚马来酰亚胺I阻断了25 mM葡萄糖诱导的[(3)H]-AA释放增加和α-MG摄取抑制。然而，新霉素、U 73122和磷脂酶c（PLC）抑制剂不阻断25 mM葡萄糖对[(3)H]-AA释放和α-MG摄取的影响。L型钙通道阻滞剂甲氧基维拉帕米预处理消除了25 mM葡萄糖诱导的[(3)H]-AA释放增加。事实上，25 mM葡萄糖增加了胞质型磷脂酶A(2)从胞质组分向膜组分的转位。总之，目前的结果表明，高糖通过激活PKC增加AA释放来抑制α-MG摄取。
