Stimulatory effect of glucose 6-phosphate on the non-mitochondrial Ca2+ uptake in permeabilized hepatocytes and Ca2+ release by inositol trisphosphate.
The relationships between Ca2+ transport and glucose-6-phosphatase activity, previously studied in isolated liver microsomes, were investigated in permeabilized hepatocytes in the presence of mitochondrial inhibitors. It was found that the addition of glucose 6-phosphate to the cells markedly stimulates the MgATP-dependent Ca2+ uptake. A progressive increase in the stimulation of Ca2+ uptake was seen with increasing amounts of glucose 6-phosphate up to 5 mM concentrations. Vanadate, when added in adequate concentrations (20-40 microM) to the hepatocytes inhibits both the glucose-6-phosphatase activity and the stimulation of Ca2+ uptake by glucose 6-phosphate, while not affecting the MgATP-dependent Ca2+ uptake. The addition of inositol 1,4,5-trisphosphate to permeabilized hepatocytes in which Ca2+ had been accumulated in the presence of MgATP and glucose 6-phosphate, results in a rapid release of Ca2+.
D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D002451:Cell Compartmentation; D002463:Cell Membrane Permeability; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005952:Glucose-6-Phosphatase / Q000378:metabolism*; D005958:Glucosephosphates / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism*; D008297:Male; D051381:Rats; D012503:Saponins / Q000494:pharmacology; D013403:Sugar Phosphates / Q000494:pharmacology*; D014639:Vanadium / Q000494:pharmacology
D005958:Glucosephosphates; D007295:Inositol Phosphates; D012503:Saponins; D013403:Sugar Phosphates; D014639:Vanadium; D015544:Inositol 1,4,5-Trisphosphate; D005952:Glucose-6-Phosphatase; D002118:Calcium