Metabolic regulation of intracellular calcium concentration in mouse pancreatic islets of Langerhans.
Intracellular Ca2+ concentration ([Ca2+]i) handling during K(+)-induced Ca2+ loads was studied in single islets of Langerhans. K(+)-induced depolarization caused a rapid and transient rise in [Ca2+]i. After K+ removal [Ca2+]i declined with a time course usually fitted by the sum of two exponential functions. Partial Na+ removal increased the resting [Ca2+]i level, indicating the existence of a Na+/Ca2+ exchange, but only slightly impaired the recovery from Ca2+ loads. Metabolic poisoning with CN- increased the resting Ca2+ level and slowed down the recovery from Ca2+ loads. Removal of external Na+ in islets poisoned with CN- strongly inhibited Ca2+ removal mechanisms. An increase in the glucose concentration from 0 to 16 mM (in the presence of diazoxide) resulted in a decrease in the resting [Ca2+]i and an acceleration of [Ca2+]i recovery from K+ loads. These results suggest that the main mechanism responsible for Ca2+ homeostasis is dependent on metabolic energy and that such energy can be provided by glucose metabolism.
Nadal
A
A
Department of Physiology, University of Alicante, Spain.
Valdeolmillos
M
M
Soria
B
B
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D003486:Cyanides / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism*; D007515:Islets of Langerhans / Q000378:metabolism* / Q000502:physiology; D008564:Membrane Potentials; D051379:Mice; D009994:Osmolar Concentration; D019831:Sodium-Calcium Exchanger
D002352:Carrier Proteins; D003486:Cyanides; D019831:Sodium-Calcium Exchanger; D005947:Glucose; D002118:Calcium