Regulation of Na+/Ca2+ exchange in the rat pancreatic B cell

• Published in: Biochemical journal Vol. 285; no. 1; pp. 123 - 127
• Main Authors: PLASMAN, P.-O, HERCHUELZ, A
• Format: Journal Article
• Language: English
• Published: Colchester Portland Press 01.07.1992
• Subjects: 2,4-Dinitrophenol; Animals; Antimycin A - pharmacology; Biological and medical sciences; Biological Transport - drug effects; Calcium - metabolism; Cations, Divalent; Cell physiology; Dinitrophenols - pharmacology; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Islets of Langerhans - metabolism; Membrane and intracellular transports; Mitochondria - drug effects; Mitochondria - metabolism; Molecular and cellular biology; Monensin - pharmacology; Oligomycins - pharmacology; Potassium - pharmacology; Rats; Sodium - metabolism; Tetradecanoylphorbol Acetate - pharmacology; Calcium; Rat; Rodentia; B-Lymphocyte; Coupled transport; Glucose; Vertebrata; Regulation(control); Mammalia; Sodium; pH; Intracellular; Pancreas
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj2850123

Na+/Ca2+ exchange in the B cell was recently characterized by measuring intracellular-Na(+)-dependent 45Ca2+ uptake in isolated rat pancreatic islet cells. The aim of the present study was to investigate the regulation of this process. Extracellular pH (pHo) and intracellular pH (pHi) markedly affected Na+/Ca2+ exchange. A fall of 0.04 unit in pHi decreased the exchange by 45%, whereas a rise of 0.13 unit increased the uptake by 70%. Mitochondrial poisons (oligomycin, antimycin A and 2,4-dinitrophenol) inhibited reverse Na+/Ca2+ exchange by about 25-50%. The exchanger displayed a low Q10 (temperature coefficient), indicating that it is only indirectly dependent on metabolic energy. The phorbol ester phorbol 12-myristate 13-acetate did not affect Na+/Ca2+ exchange. Likewise, lowering the extracellular K+ concentration did not inhibit 45Ca2+ uptake. In conclusion, the pHi and the metabolic state of the cell may represent important modulatory signals by which insulin secretagogues such as glucose could regulate reverse Na+/Ca2+ exchange in the B cell. The process does not appear to co-transport K+ nor to be influenced by protein kinase C.