title: Stimulation of Na+/H+ antiport and pyruvate kinase activities by high glucose concentration in human erythrocytes.
abstract: This study aims to demonstrate the effect of high glucose concentrations on NHE-1 and PK activities and investigate the implicated signal transduction pathways. Erythrocytes drawn from healthy volunteers were incubated in the presence of 5 or 50 mM of glucose, fructose, galactose or mannitol. When appropriate, specific inhibitors of NHE-1, PKC or p42/44 MAPK were used. Erythrocyte NHE-1 activity has been estimated by fluorometrical determination of the intracellular pH and quantification of sodium uptake using 22Na. Pyruvate kinase activity was measured by a NADH-lactate dehydrogenase enzymatic assay. p42/44 MAPK activity was assessed with a specific enzyme linked immunosorbent assay (ELISA). Increased concentrations of glucose but not galactose, fructose or mannitol enhanced erythrocyte NHE-1, PK and p42/44 MAPK activity. Inhibition of PKC, counteracted these effects of glucose. Similarly, inhibition of NHE 1 abolished the effect of high glucose on PK and p42/44 MAPK as well. Finally, inhibition of p42/44 MAPK also hindered the effect of glucose on NHE-1 and PK activities. The data of the present study indicate an acute effect of glucose on signal transduction pathways in human erythrocytes. This pathway involves NHE-1, PKC, and p42/44 MAPK. A positive feedback between NHE 1 and p42/44 MAPK is suggested.
authors.affiliation: Department of Biological Chemistry, Medical School, Aristotle University, Thessaloniki 54124, Greece.
authors.forename: Martha
authors.initials: M
authors.lastname: Kaloyianni
authors.forename: Nikos
authors.initials: N
authors.lastname: Tsagias
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Liakos
authors.forename: Zacharoula
authors.initials: Z
authors.lastname: Zolota
authors.forename: Euthymios
authors.initials: E
authors.lastname: Christophorides
authors.forename: George G
authors.initials: GG
authors.lastname: Koliakos
mesh_terms: D001786:Blood Glucose / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004912:Erythrocytes / Q000378:metabolism*; D006601:Hexoses / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D045022:Lactate Dehydrogenases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D011770:Pyruvate Kinase / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D004791:Enzyme Inhibitors; D006601:Hexoses; D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1; D045022:Lactate Dehydrogenases; D011770:Pyruvate Kinase; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases