本實驗主要是研究 L-arginine 對哺乳類耳蝸外毛細胞慢運動性之影響. L-arginine (3 mM) 會導致耳蝸外毛細胞的延長, 但 D-arginine (3 mM)或其它的胺基酸 (L-aspartate or L-glutamate) 並不影響. 相似的, cGMP 穿膜相似衍生物, 8-(4-chlorophenylthio)guanosine 3’:5’-cyclic monophosphate (1 mM) 或 8-bromo-guanosine 3’:5’-cyclic monophosphate (1 mM) 也可引發天竺鼠耳蝸毛細胞的延長. L-arginine 引發毛 細胞的延長的作用可被一氧化氮合成酵素抑制劑 NG-nitro-L-arginine methyl ester hydrochloride (3 mM) or 7-nitroindazole (1 mM) 所阻斷. 比較 L-arginine與 ionomycin 在細胞長度與細胞內鈣的作用, L-arginine 與 ionomycin 皆可造成天竺鼠耳蝸外毛細胞的延長, 但L-arginine不會引起細胞內鈣離子濃度的變化. 將外毛細胞前處理EGTA (3 mM) 40 分鐘以變降低細胞外鈣濃度並不會影響L-arginine的作用. 這個實驗證明一氧化氮/cGMP 路徑參與調控哺乳類耳蝸外毛細胞慢運動性的可能性. 而 L-arginine 的作用是非鈣依賴性.
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.
