Developmental changes in the structure of perinatal ruminal epithelium: Basal infoldings,glycogen, and glycocalyx

Summary The rumen of fetal, 12 hour, and 3 day lambs is lined by a non-keratinized epithelium about 400 thick which contains a high concentration of glycogen. By 7 days after birth the epithelium is considerably thinner, contains only traces of glycogen, and resembles the keratinizing epithelium of the adult. No glycogen is found in the keratinizing epithelium of 33–35 day lambs. A PAS reactive glycocalyx is seen first on keratinizing cells in epithelium of the 7 day lamb and is noted in ruminal epithelium of all older animals. The basal surface of the epithelium in the fetus and newborn is smooth. Scattered infoldings are seen on the same surface in 7 and 33–35 day lambs; the basal surface of adult ruminal epithelium is covered by microvillous processes. Differentiation of a glycocalyx and a large basal surface area are indicative of the developing transport function of the epithelium.The observations which form the basis of this publication were made in the Division of Animal Physiology, C.S.I.R.O., Prospect, N.S.W., Australia. Partial support was derived from a grant to Columbia University (GM-15289) from the National Institute of General Medical Sciences, United States Public Health Service.