Structure and histochemistry of the normal intestine of the fowl. I. The mature absorptive cell

The fine structure and cytochemistry of the intestinal epithelial cell of the fowl have been investigated. The fine structure of the mature absorptive cell of the fowl duodenum was very similar to that described for man and other mammals. Minor differences were the thinner microvillous glycocalyx, the unusual length of the cells and their microvilli, and the wide distribution of lysosomal bodies. The membrane-associated enzymes alkaline phosphatase, ATPase (pH 7.2) and leucine naphthylamidase were mainly associated with the brush border; this organelle also gave positive reactions for mucopolysaccharides and phospholipids. No enzyme activities were found in the terminal web. The distribution of lysosomes between the terminal web and the Golgi apparatus was correlated with the granular localization of the lysosomal enzymes acid phosphatase, β-glucuronidase and non-specific esterase. The mitochondrial enzyme succinate dehydrogenase was seen to be localized in rod-like dots which marked the distribution of mitochondria in the absorptive cell. The localization of mitochondrial ATPase (pH 9.4) was not clearly demonstrated because of diffusion artifacts. The region of the Golgi apparatus gave a strong reaction for thiamine pyrophosphatase, together with weak reactions for acid and alkaline phosphatases after extensive overincubation. The endoplasmic reticulum-associated enzymes glucose-6-phosphatase and nonspecific esterase were distributed throughout the absorptive cell, with a maximum activity apical to the Golgi apparatus. Additionally, the jejunal absorptive cells showed endoplasmic reticulum-as well as lysosomal-associated β-glucuronidase.