AI Article Synopsis
- The study investigates the presence of calcium-activated potassium channels in chondrocytes, revealing that an increase in extracellular calcium concentration leads to a rise in intracellular calcium levels.
- Using fura-2 staining, it was found that increasing extracellular calcium from 0.1 to 2 mM raised intracellular calcium significantly, a response that can be inhibited by La3+.
- Patch clamp experiments confirmed that higher intracellular calcium increases the likelihood and current flow through potassium channels, indicating that these channels are responsive to calcium levels in chondrocytes.
Article Abstract
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.
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