| 9627094 |
Chan HC, Lui KM, Wong WS, Poon AM: Effect of melatonin on chloride secretion by human colonic T84 cells. Life Sci. 1998;62(23):2151-8.
The effect of melatonin on human colonic T84 cells was studied using the short-circuit current (I (SC)) technique. Basolateral, as well as apical, addition of melatonin stimulated I (SC) in a concentration-dependent manner (EC50 at about 100 microM). The I (SC) response to melatonin was nearly abolished when external Cl- was removed. The increase in I (SC) was also blocked by apical addition of two Cl- channel blockers, 4,4'-diisothiocyanatostibene-2,2'-disulfonic acid (DIDS) and diphenylamine-2-carboxylic acid (DPC), indicating that melatonin stimulated Cl- secretion. The effect of different melatonin analogs was compared and the order of potency appeared to be 2-iodomelatonin > melatonin > 6-hydroxymelatonin, indicating the involvement of melatonin receptors. However, inhibitors for Gi-protein, adenylate cyclase or phospholipase C were found to be ineffective in inhibiting the melatonin-induced I (SC). Pretreatment of the cells with melatonin was also found to exert little effect on subsequent forskolin- or VIP-induced I (SC), further excluding its interaction with adenylate cyclase. Our data suggest that melatonin may play a role in regulating colonic Cl- secretion via melatonin receptors; however, the signal transduction pathway (s) involved remains to be elucidated. |
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