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Abstract

The effect of L-arginine on the slow motility of mammalian cochlear outer hair cells was studied in this experiment. L-Arginine (3 mM) but not D-arginine (3 mM) or other amino acids (L-aspartate or L-glutamate) induced length increases of guinea pig outer hair cell. Similarly, the membrane-permeant cGMP analogues, 8-(4-chlorophenylthio)guanosine 3′:5′-cyclic monophosphate (1 mM) or 8-bromo-guanosine 3′:5′-cyclic monophosphate (1 mM) induced length increases of guinea pig outer hair cells. These length increases induced by L-arginine can be attenuated by a 30 min preincubation of the cells with the nitric oxide synthase inhibitors NG-nitro-L-arginine methyl ester hydrochloride (3 mM) or 7-nitroindazole (1 mM). Comparing the effects of L-arginine and ionomycin on cell length and intracellular calcium change in outer hair cells, both L-arginine and ionomycin were able to induce the elongation of outer hair cells but L-arginine did not change the fluorescence intensity of Fluo-3. Preincubation of the cells with EGTA (3 mM) for 40 min to reduce the extracellular calcium concentration did not influence the effect of L-arginine. This experiment demonstrated that nitric oxide/cGMP pathway involvement in regulating the slow motility of mammalian outer hair cells cannot be ruled out. The effect of L-arginine is independent of extracellular calcium concentration.