Transfer of Phosphate in the Digestive Tract II. Sheep

Abstract

The distribution of intravenously injected radiophosphorus among the contents of the sheep digestive tract indicates a mineral exchange between these materials and the blood. This exchange for phosphorus was more active than that previously observed in swine and involved different secretory sites. Phosphate, which may function as a buffer for volatile fatty acids produced in the rumen, enters the rumen via the saliva, and in apparently even larger quantities directly through the rumen wall. A rapid increase in radioactivity of the omasal contents indicates phosphorus secretion in this organ. The principal site of endogenous phosphorus secretion seems to be the ruminant stomach, and very little phosphorus enters the intestines. An early appearance of radioactivity of the rectal contents indicates a small but active secretion of phosphorus in this region. A pronounced aging effect is noted in the phosphorus exchange of the gastrointestinal tissues of sheep. Aging in sheep, however, does not lead to change in chemical composition of the body as it does in swine.