| Research Abstract |
Nitric oxide (NO) is produced from various types of cells including airway epithelial cells and plays an important role in physiologic and inflammatory processes in the airway. In this study, NO production from cultured epithelial cells was measured at real time by NO selective microsensor, polarographically. This study was aimed to determine the role of NO in the airway epithelium.
1.NO production from airway epithelium
Airway epithelial cells from cow trachea produced NO spontaneously. Isoproterenol (ISO) and dibutylyl cyclic AMP stimulated NO production. This response was inhibitted by L-NG-nitroarginine methylester (L-NAME). In contrast, ATP and bradykinin (BK) had little effect on NO production. These data suggest that NO production from airway epithelium is mediated via cyclic AMP.
2.The effect of NO on Ca^<2+> dynamics
L-NAME did not change baseline level of intracellular calcium ([Ca^<2+>]i). However, pretreatment of the cells with L-NAME,but not D-NAME,inhibited ATP-and BK-induced increase in [Ca^<2+>]i. This inhibitory effect was reversed by L-arginine.
Furthermore, pretreatment of the cells with nitroprusside and dibutyryl cyclic GMP potentiated ATP-and BK-induced increase in [Ca^<2+>]i. These results suggest that endogenous and exogenous NO affect Ca^<2+> dynamics in the airway epithelium.
3.The effect of NO on Cl secretion
The cell sheets ware mounted in Ussing chamber in the presence of amiloride to assess active Cl secretion. Short circuit current (Isc) was continuously monitored. L-NAME alone induced little decrease in Isc. Pretreatment of the cells with L-NAME,but not D-NAME,strongly inhibited ATP-, BK-and ISO-induced increases in Isc. This L-NAME-induced suppression was dose-dependent and reversed by the simultaneous addition of L-arginine. These data suggest that endogenous NO is a key molecule for agonist-induced Cl secretion.
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