Glucose-induced oscillations in cytoplasmic free Ca2+ concentration precede oscillations in mitochondrial membrane potential in the pancreatic beta-cell.
Using dual excitation and fixed emission fluorescence microscopy, we were able to measure changes in cytoplasmic free Ca(2+) concentration ([Ca(2+)](i)) and mitochondrial membrane potential simultaneously in the pancreatic beta-cell. The beta-cells were exposed to a combination of the Ca(2+) indicator fura-2/AM and the indicator of mitochondrial membrane potential, rhodamine 123 (Rh123). Using simultaneous measurements of mitochondrial membrane potential and [Ca(2+)](i) during glucose stimulation, it was possible to measure the time lag between the onset of mitochondrial hyperpolarization and changes in [Ca(2+)](i). Glucose-induced oscillations in [Ca(2+)](i) were followed by transient depolarizations of mitochondrial membrane potential. These results are compatible with a model in which nadirs in [Ca(2+)](i) oscillations are generated by a transient, Ca(2+)-induced inhibition of mitochondrial metabolism resulting in a temporary fall in the cytoplasmic ATP/ADP ratio, opening of plasma membrane K(ATP) channels, repolarization of the plasma membrane, and thus transient closure of voltage-gated L-type Ca(2+) channels.
Kindmark
H
H
Rolf Luft Center for Diabetes Research, Department of Molecular Medicine, Karolinska Institutet, Karolinska Hospital, S-171 76 Stockholm, Sweden. henrik.kindmark@ks.se
Köhler
M
M
Brown
G
G
Bränström
R
R
Larsson
O
O
Berggren
P O
PO
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D003593:Cytoplasm / Q000378:metabolism*; D005260:Female; D005453:Fluorescence; D005947:Glucose / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D020112:Rhodamine 123 / Q000494:pharmacology
D009243:NAD; D020112:Rhodamine 123; D000255:Adenosine Triphosphate; D005947:Glucose; D002118:Calcium