The uptake of ferritin by ileal absorptive cells in suckling rats. an electron microscope study

Abstract

Abstract An electron microscopic study of the small intestine of rats from birth to 15 days of age has demonstrated a gradient of both structure and function along the length of the small intestine. During this period of development, only the ileum was found to absorb intact exogenous ferritin or colostral proteins. In newborn rats ferritin particles or milk proteins are incorporated by ileal absorptive cells into tubular invaginations of the apical plasmalemma which connect with vacuoles or cisternae in the apical cytoplasm. The ferritin particles are then transported by another vacuolar system to the supranuclear region where several such vacuoles coalesce to form a single supranuclear vacucle. After the first feeding the supranuclear vacuole is established in the ileal cells so that additional ingested proteins, whether ferritin or from milk, are transported from the cisternae directly to the supranuclear vacuole. There was no evidence in the present study to indicate that ferritin is transmitted from the ileal cell to the circulation. The subject of protein transport by the intestinal epithelium is reviewed briefly.