Linoleic acid induces Ca2+-induced inactivation of voltage-dependent Ca2+ currents in rat pancreatic beta-cells.
Free fatty acids (FFAs) regulate insulin secretion in a complex pattern and induce pancreatic beta-cell dysfunction in type 2 diabetes. Voltage-dependent Ca2+ channels (VDCC) in beta-cells play a major role in regulating insulin secretion. The aim of present study is to clarify the action of the FFA, linoleic acid, on VDCC in beta-cells. The VDCC current in primary cultured rat beta-cells were recorded under nystatin-perforated whole-cell recording configuration. The VDCC was identified as high-voltage-gated Ca2+ channels due to there being no difference in current amplitude under holding potential between -70 and -40 mV. Linoleic acid (10 microM) significantly inhibited VDCC currents in beta-cells, an effect which was fully reversible upon washout. Methyl-linoleic acid, which does not activate G protein coupled receptor (GPR)40, neither did alter VDCC current in rat beta-cells nor did influence linoleic acid-induced inhibition of VDCC currents. Linoleic acid-induced inhibition of VDCC current was not blocked by preincubation of beta-cells with either the specific protein kinase A (PKA) inhibitor, H89, or the PKC inhibitor, chelerythrine. However, pretreatment of beta-cells with thapsigargin, which depletes intracellular Ca2+ stores, completely abolished linoleic acid-induced decrease in VDCC current. Measurement of intracellular Ca2+ concentration ([Ca2+](i)) illustrated that linoleic acid induced an increase in [Ca2+](i) and that thapsigargin pretreatment inhibited this increase. Methyl-linoleic acid neither did induce increase in [Ca2+](i) nor did it block linoleic acid-induced increase in [Ca2+](i). These results suggest that linoleic acid stimulates Ca2+ release from intracellular Ca2+ stores and inhibits VDCC currents in rat pancreatic beta-cells via Ca2+-induced inactivation of VDCC.
Feng
Dan-Dan
DD
Department of Physiology, Xiangya Medical School, Central South University, Changsha, 410078 People's Republic of China.
Zhao
Yu-Feng
YF
Luo
Zi-Qiang
ZQ
Keating
Damien J
DJ
Chen
Chen
C
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects* / Q000502:physiology*; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004553:Electric Conductivity; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism*; D019787:Linoleic Acid / Q000494:pharmacology*; D008042:Linolenic Acids / Q000494:pharmacology; D008297:Male; D009994:Osmolar Concentration; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D019284:Thapsigargin / Q000494:pharmacology
D015220:Calcium Channels; D004791:Enzyme Inhibitors; D004963:Estrenes; D008042:Linolenic Acids; D011760:Pyrrolidinones; C047376:methyl linolenate; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D019284:Thapsigargin; D019787:Linoleic Acid; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D002118:Calcium