Caffeine-induced shortening of isolated outer hair cells: an osmotic mechanism of action.
The application of caffeine to the bathing medium of isolated cochlear outer hair cells (OHCs) induces shortening of the cells (Slepecky et al., 1988). This study was designed to test the hypothesis that a 'smooth muscle-like' mechanism was responsible for the caffeine-induced shortening of OHCs as suggested by Slepecky et al. OHCs were isolated from guinea pig cochleae and length measurements were taken during various drug perfusions. Antagonists of the ryanodine receptor/Ca(2+)-induced Ca2+ release (CICR; tetracaine, ruthenium red, and ryanodine) failed to block the caffeine-induced shortening of the OHCs. Application of the Ca2+ ionophore A23187 caused cell length to increase. These results did not support this hypothesis and therefore, an osmotic mechanism was proposed.
Skellett
R A
RA
Kresge Hearing Research Laboratory of the South, Department of Otorhinolaryngology and Biocommunication, Louisiana State University Medical Center, New Orleans 70112, USA.
Crist
J R
JR
Fallon
M
M
Bobbin
R P
RP
D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D000001:Calcimycin / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects*; D003051:Cochlea / Q000187:drug effects; D005260:Female; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects*; D008297:Male; D009124:Muscle Proteins / Q000187:drug effects* / Q000378:metabolism; D009994:Osmolar Concentration; D010477:Perfusion; D012430:Ruthenium Red / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel; D013748:Tetracaine / Q000494:pharmacology
D015220:Calcium Channels; D009124:Muscle Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D013748:Tetracaine; D012430:Ruthenium Red; D012433:Ryanodine; D000001:Calcimycin; D002110:Caffeine