title: 12-HETE modulates Na-coupled uptakes in proximal tubular cells: role of diacylglycerol kinase inhibition.
abstract: Inhibition of diacylglycerol (DAG) kinase, an alternative way to increase the cellular DAG level, was shown to reproduce, in renal proximal tubular cells, the inhibitory effect of protein kinase C (PKC) activators on Na-Pi and Na-alpha-methyl-D-glucopyranoside (MGP) cotransport. To evaluate whether 12S-hydroxyeicosatetraenoic acid (12S-HETE) or 12R-HETE, a DAG kinase inhibitor in endothelial cells, has a similar effect in proximal tubular cells, we studied the influence of this lipoxygenase product on Na-dependent uptake of Pi, MGP, and alanine, as well as on [14C]arachidonate-DAG content and [32P]phosphatidic acid (PA) content in rabbit proximal tubular cells grown as a primary culture. 12-HETE (1-10 microM) decreased [32P]PA content and stimulated [14C]DAG accumulation in a concentration-dependent manner. The labeled phosphatidylcholine, lysophosphatidylcholine, and sphingomyelin contents were not modified. 12-HETE also decreased DAG kinase activity of cell membranes. 12-HETE (10 microM) decreased the maximum velocity of Pi uptake by 36% and that of MGP uptake by 44% but did not affect alanine uptake. The effect of 12-HETE on transport was potentiated by calcium ionophore A23187 and was blunted by PKC downregulation. The effects of 12-HETE on lipid composition and transport were mimicked by R 59022, a pharmacological DAG kinase inhibitor. Neither arachidonic acid nor prostaglandin E2 reproduced the effects of 12-HETE. We conclude that in the proximal tubule, 12-HETE affected Na-dependent Pi and MGP cotransport through stimulation of PKC and that 12-HETE-induced activation of PKC is mediated by the inhibition of DAG kinase.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 251, Faculté de Médecine Xavier-Bichat, Université Paris, France.
authors.forename: G
authors.initials: G
authors.lastname: Friedlander
authors.forename: C
authors.initials: C
authors.lastname: Le Grimellec
authors.forename: J
authors.initials: J
authors.lastname: Sraer
authors.forename: C
authors.initials: C
authors.lastname: Amiel
mesh_terms: D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D026905:Amino Acid Transport Systems; D026921:Amino Acid Transport Systems, Neutral; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D019852:Diacylglycerol Kinase; D004075:Diglycerides / Q000378:metabolism; D006893:Hydroxyeicosatetraenoic Acids / Q000494:pharmacology*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D010712:Phosphatidic Acids / Q000378:metabolism; D010770:Phosphotransferases / Q000037:antagonists & inhibitors*; D012964:Sodium / Q000378:metabolism; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters
chemical_list: D026905:Amino Acid Transport Systems; D026921:Amino Acid Transport Systems, Neutral; D002352:Carrier Proteins; D004075:Diglycerides; D006893:Hydroxyeicosatetraenoic Acids; D010712:Phosphatidic Acids; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters; C052168:sodium-alanine cotransporter; D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D012964:Sodium; D010770:Phosphotransferases; D019852:Diacylglycerol Kinase