Acute gentamicin ototoxicity in cochlear outer hair cells of the guinea pig.

The acute effects of the aminoglycoside antibiotics gentamicin on isolated cochlear outer hair cells (OHC) was investigated by whole-cell patch-clamp and measurements of the intracellular potassium level by means of the potassium-sensitive dye PBFI. In addition, the accompanying length changes of OHC are described. It could be shown that gentamicin at different concentrations reversibly induces a hyperpolarization by about 5-10 mV, potassium outflow from the cytoplasm (by about 22 mM) and a cellular elongation (by about 10%). It is suggested that these effects are the result of an interaction between gentamicin and the cochlear transduction channels in OHC as suggested earlier. These acute effects are distinctly different from the chronic gentamicin effects which are based on the metabolization of the antibiotics to cause the death of the OHC by interaction with the phosphoinositide signalling cascade.