Transport of fatty acid mixtures across rumen epithelium.

STEVENS, C. E., AND B. K. SETTLER. Transport offatty acid mixturesacross rumen epithelium. Am. J. Physiol. 2 I I ( I) : R264-27 I. rg66.-Transport of acetate and propionate was affected by the presence of other fatty acids. Acetate appeared to be utilized by the tissue more rapidly when propionate was present and was produced by conversion from butyrate. Propionate transport was greater when acetate and butyrate were also present. Fatty acid transport was relatively unaffected by decreasing the PotL and increasing the Pcoz of the lumen bath at a constant pH, but these changes did result in a marked reduction in the appearance of ketone bodies. They also resulted in a decreased short-circuit current and tissue resistance. The decrease in short-circuit current was primarily due to the decrease in lumen bath Paz and apparently represented an inhibition of active ion transport. An applied electrical potential gradient, favoring anion transport, did not increase the transport of the three fatty acids. A study of the effects of electrochemical difference on acetate transport indicated that, unless other mechanisms were involved, the tissue was relatively impermeable to the acetate anion. Extrapolation of transport data obtained under conditions similar to those found in vivo gave values lower than those which might be expected in the living animal.