Glucose metabolism by rat pancreatic beta-cells produces dual change in cytosolic Ca2+.
It was reported that glucose stimulation initially lowers as well as subsequently raises the cytosolic free calcium concentration ([Ca2+]i) in pancreatic islet cells from hyperglycemic ob/ob mice. In the present study, [Ca2+]i in single pancreatic beta-cells from normal rats was measured by fura-2 microfluorometry. Following elevation of the glucose concentration to 16.7 mM from either 2.8 mM (basal) or 5.6 mM, an initial decrease and subsequent increase in [Ca2+]i were demonstrated. An elevation of the glucose concentration from 2.8 to 5.6 mM induced the decrease in [Ca2+]i but not usually the increase. Removal of extracellular Ca2+ eliminated the increase in [Ca2+]i without affecting the decrease. Mannoheptulose and KCN, inhibitors of glucose metabolism and TCA cycle, eliminated both the decrease and increase in [Ca2+]i. These results demonstrate that the glucose-induced bimodal change in [Ca2+]i is a physiological response of islet beta-cells, and that the decrease and increase in [Ca2+]i are generated by mutually-independent mechanisms which are operated through glucose metabolism by islet beta-cells.
Yada
T
T
Department of Physiology, Kagoshima University School of Medicine, Japan.
Itoh
K
K
Kakei
M
M
Tanaka
H
H
D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D002021:Buffers; D002118:Calcium / Q000378:metabolism*; D003486:Cyanides / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism*; D005470:Fluorometry; D016257:Fura-2; D005947:Glucose / Q000378:metabolism*; D066298:In Vitro Techniques; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008356:Mannoheptulose / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
D001639:Bicarbonates; D002021:Buffers; D003486:Cyanides; D008356:Mannoheptulose; D005947:Glucose; D002118:Calcium; D016257:Fura-2