Taicatoxin inhibits the calcium-dependent slow motility of mammalian outer hair cells.
The effects of taicatoxin on the slow motility of isolated outer hair cells of guinea pig were studied in the experiments. Pretreatment with taicatoxin (0.19 microM) was able to prevent both the cell shortening induced by high K(+) (50mM), and the cell elongation induced by ionomycin (10 microM). These effects of taicatoxin can be mimicked by pretreatment of cells with Ca(2+)-free medium on the slow motility in response to ionomycin or high K(+). Pretreatment with neither calcium channel blockers such as nifedipine (L-type blocker), omega-conotoxin GVIA (N-type blocker), and omega-agatoxin IVA (P-type blocker); nor potassium channel blockers, such as tetraethylammonium chloride (TEA) and 3,4-diaminopyridine (3,4-DAP) can antagonize the cell shortening effect induced by high K(+) and cell elongation induced by ionomycin. The calcium-imaging experiment indicated that taicatoxin, but not nifedipine, did prevent an increase of intracellular Ca(2+) level significantly induced by high K(+). These results demonstrate that the effect of taicatoxin was to block the calcium entry through calcium channels of cell membrane, without relative to its properties of potassium channel blockers. We conclude that taicatoxin-sensitive-calcium channels at least impart, play a significant role in the slow motility of outer hair cell.
Su
Mao-Chang
MC
Department of Otolaryngology, Chung Shan Medical University Hospital, Taiwan.
Lee
Shiann-Yann
SY
Tan
Ching-Ting
CT
Su
Ching-Chyuan
CC
Li
Shuan-Yow
SY
Lin
Ruey-Hseng
RH
Hung
Chui-Chen
CC
Lin
Min-Jon
MJ
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002465:Cell Movement / Q000187:drug effects* / Q000502:physiology*; D003035:Cobalt / Q000494:pharmacology; D003470:Culture Media / Q000737:chemistry / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004546:Elapid Venoms / Q000494:pharmacology*; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000502:physiology*; D007425:Intracellular Membranes / Q000378:metabolism; D015759:Ionomycin / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D011188:Potassium / Q000008:administration & dosage / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology
D002121:Calcium Channel Blockers; D003470:Culture Media; D004546:Elapid Venoms; D026902:Potassium Channel Blockers; C079205:taicatoxin; D003035:Cobalt; D015759:Ionomycin; C018021:cobaltous chloride; D009543:Nifedipine; D011188:Potassium; D002118:Calcium