Intracellular calcium and outer hair cell electromotility.
The influence of increased intracellular calcium level on outer hair cell (OHC) electromotility was examined by means of transcellular electrical stimulation in a partitioning microchamber. Electromotile activity was measured before and after application of the calcium ionophore ionomycin, which promotes the inflow of extracellular calcium, as well as its release from intracellular calcium stores. The ionomycin solvent, dimethyl sulphoxide (DMSO), by itself elicited a significant decrease in the magnitude of OHC electromotility. The DMSO effect was counteracted by 10 microM ionomycin and was reversed by 50 microM ionomycin. The increase in electromotility is partially mediated by a calmodulin-dependent mechanism, since W7, a calmodulin antagonist, attenuated the 50 microM ionomycin-induced motility increase. Our results suggest that the electromotility magnitude increase in isolated OHCs due to ionomycin is a calcium/calmodulin-dependent phenomenon.
Szönyi
M
M
Auditory Physiology Laboratory, Departments of Communication Sciences and Disorders, Frances Searle Building, Northwestern University, 2299 North Campus Drive, Evanston, IL 60208, USA.
He
D Z
DZ
Ribári
O
O
Sziklai
I
I
Dallos
P
P
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002465:Cell Movement / Q000187:drug effects; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology
D002147:Calmodulin; D004791:Enzyme Inhibitors; D007476:Ionophores; D013449:Sulfonamides; D015759:Ionomycin; C017967:W 7; D002118:Calcium; D004121:Dimethyl Sulfoxide