Fig. 2. Occludin and Na⁺,K⁺-ATPase immunolocalization in cross-sections of Xenopus (A) stomach, (B) anterior intestine, (C) posterior intestine and (D) rectum. Occludin (red) immunolocalized to apicolateral membranes of surface epithelial cells lining the stomach mucosa and enterocytes of the small intestine and rectum. Enhanced occludin immunostaining was also observed in the stomach between cells at the base of the gastric pits (arrow). Na⁺,K⁺-ATPase (green) was undetectable in the stomach but immunolocalized basolaterally in the small intestine and rectum. Control sections, probed with secondary antibody only, are shown in E and F for the stomach and rectum, respectively. L, lumen. Scale bars, 20 µm.