Oertzenweg 19 b
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Large quantities of SCFA are absorbed from the ruminant forestomach mostly unmetabolized to serve as the major source of energy in these animals. Basolateral efflux has to be protein-mediated, and a recent study suggests that the efflux of acetate from the rumen involves a 350 pS, large-conductance anion channel. Using both the whole cell and the single channel patch clamp technique, we demonstrate that this channel also has a considerable permeability for propionate. Whole cell currents were sensitive to DIDS and pCMB, but not to glibenclamide. A certain, DIDS-sensitive conductance for butyrate could also be observed, but it was significantly lower. Cells of the omasum were isolated via a novel technique and displayed similar properties, with conductance for acetate about half of that for choride. As for the anion channel of the rumen, the conductance was sensitive to DIDS. We propose a role for the large conductance anion channel in the basolateral efflux of acetate and propionate from the rumen and the omasum, with butyrate mostly metabolized.