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Journal of Korean Neurosurgical Society 1999;28(9): 1272-1281. |
| The Effect of Activation of Protein Kinase C on the Calcium-dependent K; Current in Rat Basilar Smooth Muscle Cells. |
| Chul Jin Kim |
| Department of Neurosurgery, Chonbuk National University School of Medicine, Chonju, Korea. |
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| ABSTRACT |
OBJECTIVE
Activation of protein kinase C(PKC) may play a certain role in the development of cerebral vasospasm.
However, this mechanism still elusive. This study was undertaken to investigate the action of protein kinase C on calcium-dependent K+ channels(KCa) and internal calcium concentration [Ca2+]i in freshly isolated smooth muscle cells.
METHODS
Whole-cell patch clamp and calcium microfluorimetry technique were used for measuring the K Ca and internal calcium concentration.
RESULTS
In patch-clamp studies, depolarization evoked an outward KCa current which is sensitive to caffeine and A23187, and shown to be blocked by TEA(tetraethylammonium) but not by glibenclamide. Activation of protein kinase C by phorbol 12-myristate 13-acetate(PMA:1-100nmol/1) and phorbol 12, 13-dibutyrate(PDB:1-100nmol/1) dose-dependently enhanced KCa current. Subsequent application of TEA(10-30mmol/1) but not glibenclamide(3-6nmol/1), in the presence of phorbol esters, reduced the potassium current activated by phorbol esters. Preincubation with 1-(5-isoquinoline sulphonyl)-2-methylpiperazine(H-7:10nmol/1), a protein kinase C inhibitor, prevented the effect of phorbol esters on KCa. In calcium microfluorimetric studies, PMA(100nmol/1) increased intracellular calcium concentration and this effect of PMA was prevented by pre-incubation of cells with H-7(10nmol/1).
CONCLUSION
These results indicate that activation of PKC increases intracellular calcium concentration and elevation of internal calcium concentration activates KCa in cerebral vascular smooth muscle cells. |
| Key Words:
Protein kinase C; Calcium-dependent potassium channel; Patch clamp; Microfluorimetry |
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