Stimulation of the human leucocyte Na+/H+ antiport by D-glucose is mediated by protein kinase C.
Leucocyte Na+/H+ antiport activity is elevated in patients with essential hypertension and Type 1 diabetes with nephropathy. To examine the effects of hyperglycemia on the Na+/H+ antiport, normal leucocytes were incubated with 25 mmol l-1 D-glucose, L-glucose or glucose-6-phosphate for two days. Leucocyte Na+/H+ antiport activity was measured by a novel double ionophore fluorimetric method for controlling intracellular pH. Only incubation with D-glucose led to an increase in Na+/H+ antiport activity of about 31%. This effect was not due to non-enzymic glycation since glucose-6-phosphate, which glycates proteins faster than D-glucose, caused no significant difference in antiport activity. Also, osmotic effects could be excluded. Staurosporine (10 nmol l-1), a specific inhibitor of protein kinase C, prevented the rise in antiport activity due to incubation with D-glucose. As hyperglycaemia is known to increase protein kinase C activity, elevation of this kinase may be one mechanism for activation of the Na+/H+ antiport in Type 1 diabetes.
Aston
C W
CW
Sheikh Rashid Diabetes Unit, Radcliffe Infirmary, Oxford, UK.
Ng
L L
LL
Garrido
M C
MC
Bomford
J
J
D000328:Adult; D000470:Alkaloids / Q000494:pharmacology; D002352:Carrier Proteins / Q000097:blood*; D005260:Female; D005947:Glucose / Q000494:pharmacology*; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D007962:Leukocytes / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000097:blood*; D012016:Reference Values; D012964:Sodium / Q000097:blood*; D017923:Sodium-Hydrogen Exchangers; D019311:Staurosporine; D013237:Stereoisomerism
D000470:Alkaloids; D002352:Carrier Proteins; D005958:Glucosephosphates; D017923:Sodium-Hydrogen Exchangers; D019298:Glucose-6-Phosphate; D012964:Sodium; D011493:Protein Kinase C; D019311:Staurosporine; D005947:Glucose