Interferon-g downregulates ion transport in murine small intestine cultured in vitro

Yoo, Dongjin, Winson Lo, Stephen Goodman, Wasif Ali, Carol Semrad, and Michael Field. Interferon-g downregulates ion transport in murine small intestine cultured in vitro. Am J Physiol Gastrointest Liver Physiol 279: G1323–G1332, 2000.—Effects of IFN-g on mammalian small intestinal ion transport were studied in vitro using incubated sheets of murine small intestine in Ussing chambers. In oxygenated standard culture medium containing hydrocortisone and antibiotics, they maintained their short-circuit current (Isc) responses to glucose and theophylline for 48 h. Histological examination revealed a 50% diminution of villus height over 36 h but no change in crypts. Height was better maintained during a 36-h incubation of small intestine from SCID mice, suggesting a role for B or T lymphocytes in villus atrophy. Exposure of small intestine to 100 U/ml IFN-g for 36 h decreased basal Isc by 40% and Isc responses to glucose and theophylline by ;70%; at 1,000 U/ml for 36 h, IFN-g inhibited these Isc responses by 90%. An inhibitor of inducible NO synthase did not reverse these effects, suggesting that they are not mediated by NO. Tissue resistance, mucosal K content, and epithelial morphology were not affected. Ouabain-sensitive ATPase activity in homogenates was inhibited 60% by IFN-g (100 U/ml for 36 h). IFN-g inhibition of Isc responses to glucose and theophylline also occurred in SCID mouse small intestine. Thus murine small intestinal sheets can be maintained viable in vitro for at least 48 h, although villus blunting develops (but less so in SCID mouse small intestine). Also, prolonged exposure to IFN-g downregulates Na-coupled glucose absorption, active Cl secretion, and Na-K-ATPase activity, effects unlikely to be mediated by enhanced NO.