Calcium-activated potassium channels in chondrocytes.
The presence of calcium-activated potassium channels in chondrocytes of growing cartilage was tested. Results obtained with fura-2 on cultured resting chondrocytes indicate that the cells respond to an elevation of extracellular calcium concentration ([Ca2+]o) from 0.1 to 2 mM increasing the intracellular concentration of the ion ([Ca2+]i) from 117 to 187 nM. This increment may be blocked by 3 microM La3+. Patch clamp experiments in cell-attached configuration showed that, when [Ca2+]i rises, the open probability (Po) of the K+ channels increases. Increments in both Po and unitary currents of the K+ channels can be obtained after applying 2.5 microM A23187 with 2 mM [Ca2+]o. Hence, the results demonstrate that, in chondrocytes, a class of Ca(2+)-activated K+ channels is present and their activity is related to an increase of [Ca2+]i.
Grandolfo
M
M
Dip Biochimica, Biofisica e Chimica delle Macromolecole, Trieste, Italy.
D'Andrea
P
P
Martina
M
M
Ruzzier
F
F
Vittur
F
F
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002358:Cartilage, Articular / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D016257:Fura-2; D007700:Kinetics; D007811:Lanthanum / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D013552:Swine
D015221:Potassium Channels; D000001:Calcimycin; D007811:Lanthanum; D002118:Calcium; D016257:Fura-2