Antisecretory effect of loperamide in colon epithelial cells by inhibition of basolateral K+ conductance

• Published in: Scandinavian journal of gastroenterology Vol. 36; no. 7; p. 731
• Main Authors: Epple, H J, Fromm, M, Riecken, E O, Schulzke, J D
• Format: Journal Article
• Language: English
• Published: England 01.01.2001
• Subjects: Antidiarrheals - pharmacology; Calcium Channel Blockers - pharmacology; Calmodulin - antagonists & inhibitors; Carbachol - pharmacology; Chlorides - physiology; Cholinergic Agonists - pharmacology; Colforsin - pharmacology; Colon - cytology; Drug Evaluation, Preclinical; Enterocytes - drug effects; Enterocytes - metabolism; HT29 Cells - drug effects; HT29 Cells - metabolism; Humans; Intestinal Mucosa - drug effects; Intestinal Mucosa - metabolism; Loperamide - pharmacology; Naloxone - pharmacology; Narcotic Antagonists - pharmacology; Potassium Channels - drug effects; Signal Transduction - drug effects; Time Factors; Trifluoperazine - pharmacology; Verapamil - pharmacology
• ISSN: 0036-5521
• DOI: 10.1080/00365520121445

The mechanism of the antisecretory effect of loperamide was investigated in cultured highly differentiated colon epithelial cells (HT-29/B6). Chloride secretion was stimulated via cAMP by forskolin (FSK, 10(-5) M), via Ca2+ by the muscarinic agonist carbachol (CCh, 10(-4) M), and via protein kinase C by the phorbol ester PMA (5 x 10(-9) M). Stimulated Cl- secretion was quantified as short circuit current (I(SC)) of HT-29/B6 monolayers mounted in Ussing-type chambers. Loperamide (5 x 10(-5) M) inhibited I(SC) stimulated by FSK, CCh and PMA. The antisecretory action of loperamide was unaffected by preincubation with naloxone (10(-5) M). Furthermore, loperamide strongly inhibited basolateral 86Rb efflux. Like loperamide, the calmodulin antagonist trifluoperazine (10(-4) M) inhibited I(SC) induced by FSK, CCh or PMA. The Ca2+ channel blocker verapamil (5 x 10(-5) M), on the other hand, inhibited only PMA-stimulated I(SC),but had no effect on FSK or CCh-induced I(SC) CONCLUSIONS: Loperamide exerts a direct antisecretory action on chloride secretion of colon epithelial cells independently of the respective stimulatory signal transduction pathway. This antisecretory effect is not mediated by opiate receptors and reflects inhibition of basolateral K+ conductance.