Regional differences in electrolyte, short-chain fatty acid and water absorption in the hindgut of two species of arboreal marsupials

Abstract

Short-chain fatty acid, electrolyte and water absorption from the hindgut of two arboreal marsupial species, the greater glider (Petauroides volans) and the brush-tail possum (Trichosurus vulpecula) were studied in vivo using a single perfusion technique. Qualitative and quantitative differences in the net movement of sodium, potassium and chloride were found between the different hindgut segments and between the two species. ALl transport processes exhibited active characteristics. Net Na+ transport in all segments was concentration-dependent in the range of 45-135 mmol . 1(-1) Na+. The proximal colon of the greater glider showed a net Na+, Cl- and water secretion and K+ absorption, all electrolyte movements being against the electrochemical gradient. Water followed passively the osmotic gradient generated mainly by the net movement of Na+. Short-chain fatty acids were absorbed according to their chain length in a constant ratio of 1.0:1.2:1.3 for acetate, propionate and butyrate, respectively. Our data indicate that absorptive and secretory processes in the hindgut of these marsupials are basically similar to those of eutherians, even in epithelia differing significantly in the direction of net solute transport.