EFFECTS OF RUMINAL HYPEROSMOLALITY ON THE ULTRASTRUCTURE OF RUMINAL EPITHELIUM AND THEIR RELEVANCE TO SODIUM TRANSPORT

¹ Division of Animal Physiology, C.S.I.R.O., Ian Clunies Ross Animal Research Laboratory, P.O. Box 239, Blacktown, N.S.W., 2148 Australia

The keratinizing epithelium of the rumen is involved in maintaining a potential difference across the rumen wall. Addition of a low dose of KCl (150-250 m-equiv) to the rumen causes an increase in the width of the intercellular spaces surrounding the basal cells; but further increase of the osmolality of the ruminal contents brings about the breakdown of the stratum granulosum and a decrease in the potential difference across the rumen wall. These changes are discussed in relation to sodium transport across the rumen wall. Zonulae occludentes have been consistently detected in the outermost layer of the stratum granulosum, and the present results indicate that these junctional complexes constitute a permeability barrier to the transepithelial movement of sodium.

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