Functional characterisation of the volume-sensitive anion channel in rat pancreatic beta-cells.
The whole-cell and perforated patch configurations of the patch-clamp technique were used to characterise the volume-sensitive anion channel in rat pancreatic beta-cells. The channel showed high permeability (P ) relative to Cl(-) to extracellular monovalent organic anions (P(SCN)/P(Cll) = 1.73, P(acetate)/P(Cll) = 0.39, P(lactate)/P(Cll) = 0.38, P(acetoacetate)/P(Cll) = 0.32, P(glutamate)/P(Cll) = 0.28) but was less permeable to the divalent anion malate (P(malate)/P(Cll) = 0.14). Channel activity was inhibited by a number of putative anion channel inhibitors, including extracellular ATP (10 mM), 1,9-dideoxyforskolin (100 microM) and 4-OH tamoxifen (10 microM). Inclusion of the catalytic subunit of protein kinase A in the pipette solution did not activate the volume-sensitive anion channel in non-swollen cells. Furthermore, addition of 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) or forskolin failed to activate the channel in intact cells under perforated patch conditions. Addition of phorbol 12,13-dibutyrate (200 nM), either before or after cell swelling, also failed to affect channel activation. Our findings do not support the suggestion that the volume-sensitive anion channel in pancreatic beta-cells can be activated by protein kinase A. Furthermore, the beta-cell channel does not appear to be subject to regulation via protein kinase C. Experimental Physiology (2001) 86.2, 145-150.
Best
L
L
Department of Medicine, University of Manchester, Oxford Road, Manchester M13 9WL, UK. lbest@central.cmht.mwest.nhs.uk
Speake
T
T
Brown
P
P
D000818:Animals; D000838:Anions / Q000378:metabolism*; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology; D005260:Female; D007473:Ion Channels / Q000378:metabolism*; D007515:Islets of Langerhans / Q000378:metabolism*; D008297:Male; D010539:Permeability; D011493:Protein Kinase C / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
D000838:Anions; D007473:Ion Channels; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C