Fig. 5

Intensity scoring of carbonic anhydrase (CA) activity in duodenum of Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB) hens (n = 10) at different ages during a production period. a Intensity scoring of carbonic anhydrase (CA) activity in duodenum. Score 1: weak or absent staining. Score 2: intermediate staining. Score 3: strong staining. Mean ± standard error. ***P < 0.001. b Duodenum of 21-week-old LB hen (score 3). Surface epithelium of villi (V) shows intense staining for CA activity in lateral cell membranes and brush border, and moderate cytosolic staining. Note capillaries with intense membrane-bound staining of endothelial cells in the lamina propria of villi. In the crypts of Lieberkühn (Cr), lateral cell membranes are intensely stained and the cytosol weak to moderately stained. In the muscularis (M), membrane-bound staining is moderate. Lumen (L). c Duodenum of 49-week-old LB hen (score 1). Surface epithelium of villi (V) shows none or very weak staining for CA activity in lateral cell membranes and moderate staining of brush border. Cytosolic staining is very weak or absent. Note capillaries with intense membrane-bound staining of endothelial cells in lamina propria of villi. No staining of cell membranes or cytosol can be seen in crypts of Lieberkühn (Cr) or smooth muscle cells of circular muscularis (M). Lumen (L), bar = 200 µm. Weak azure blue counterstain in both images