Effect of enterotoxigenic Escherichia coli (ETEC) K88 challenge on intestinal Na-K-Cl cotransporter (NKCC1) expression in young piglets. Piglets in the control group were fed the basal diet and challenged with sterile PBS. Piglets in the ETEC K88 group were fed the basal diet and challenged with ETEC K88. The middle portions of the jejunum, ileum, and colon were collected for immunohistochemistry analysis (A). The immunostaining intensity of NKCC1 (B) in the jejunum, ileum, and colon was quantified by ImageJ software (version 1.50; National Institutes of Health, Bethesda, MD). The relative mRNA expression of NKCC1 in the jejunum, ileum, and colon was determined by the 2−ΔΔCT method (C). Original magnification 100x. Scale bar = 100 μm. Results are mean ± SEM (n = 6). a,bMeans with different superscripts between columns differ (P < 0.05).