Ca(2+)-inactivated K+ current is modulated by endothelin-1 in B-16 murine melanoma cells.
It is well established that endothelin-1 (ET-1) plays a role in differentiation and proliferation in a variety of cells such as fibroblasts and human melanoma cells via a receptor-mediated mechanism. However, whether ET-1 modulates ion channel activity in these cell types is still unknown. In this report, we recorded the voltage-dependent outward K+ current in cultured B16 melanoma cells using the patch-clamp technique. Biophysical and pharmacological properties of the K+ current, and the effect of ET-1 on the K+ current were investigated. When cells were loaded with a Ca(2+)-chelating agent (EGTA or BAPTA), the K+ current amplitude gradually increased with time after establishment of the whole cell configuration. Replacement of Ca2+ with Co2+ in the extracellular medium caused no significant modulation of the K+ current amplitude. Addition of BaCl2 or quinidine to the extracellular solution reduced the K+ current amplitude, whereas the K+ current was insensitive to tetraethylammonium. ET-1 (10 nM) reversibly decreased the K+ current amplitude and accelerated the decay of the K+ current. The ET-1-induced inhibitory effect displayed no desensitization following repeated ET-1 application. Pretreatment with pertussis toxin (PTX) or perfusion of cells with the protein kinase C (PKC) inhibitor H-7 abolished the inhibitory effect of ET-1 on the K+ current. We conclude that the outward K+ current recorded in murine B-16 melanoma cells represents a Ca(2+)-inactivated K+ current, and that the inhibitory effect of ET-1 on the K+ current may reveal a novel mechanism to control the differentiation and proliferation of melanoma cells.
Ma
Lai-Ji
LJ
Department of Research and Development, Shanghai Jahwa United Company Ltd, Shanghai, China.
Liu
Lin-Yun
LY
Jiao
Song
S
Wei
Shao-Ming
SM
Mei
Yan-Ai
YA
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000502:physiology; D045744:Cell Line, Tumor; D003035:Cobalt; D004533:Egtazic Acid / Q000494:pharmacology; D019332:Endothelin-1 / Q000037:antagonists & inhibitors / Q000502:physiology*; D006801:Humans; D008546:Melanoma, Experimental / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D037342:Pertussis Toxin / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism
D019332:Endothelin-1; D026902:Potassium Channel Blockers; D024681:Potassium Channels, Calcium-Activated; D003035:Cobalt; D004533:Egtazic Acid; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D037342:Pertussis Toxin; D011493:Protein Kinase C; D002118:Calcium