Mechanisms of Organic Acid and Monosaccharide Transport in the Kidney of the Brush-tailed Possum, Trichosurus vulpecula

The mechanisms of organic acid and monosaccharide transport in the kidney of T. vulpecula were investigated using the renal cortical slice preparation. The kinetics, the sensitivity to inhibitors of metabolism and sodium transport, and the specificity of the concentrative uptake of p-aminohippurate and oc-methyl-n-glucoside were examined and compared with published results from studies in eutherian mammals. Some minor differences between metatherians and eutherians were noted with regard to the specificities of the renal slice uptake systems. Penicillin G, a competitor of organic acid transport in eutherian kidneys, did not interact with the marsupial uptake system, and sodium acetate, which stimulates transport in other mammals, inhibited p-aminohippurate uptake in the slice of the possum kidney. 2-Deoxy-n-glucose, which interacts with the phlorizinsensitive monosaccharide transport system in the dog, rat and rabbit kidney, had no effect on oc-methyl-n-glucoside uptake in the possum, and the magnitude of the interaction of n-fructose resembled that reported in the dog and rat but was greater than the inhibition reported in the rabbit. n-Glucuronic acid and n-glucuronic acid lactone inhibited oc-methyl-n-glucoside uptake in the possum but had no effect on uptake in rat renal slices. In consideration of the reported variability of these parameters between different classes of eutherians, it was concluded that the primary mechanisms involved in organic solute transport by the proximal nephron of metatherians and eutherians were not significantly different.