AMINO ACID TRANSPORT IN RAT RENAL PAPILLA

The uptake of amino acids in slices of renal papilla of rats has been investigated in vitro under environmental conditions of high sodium and non-electrolyte concentrations and low O2 tensions, and compared with uptake under similar conditions in slices of renal cortex. l-Lysine, cycloleucine and α-aminoisobutyric acid were actively concentrated in Krebs-Ringer-bicarbonate buffer up to 8 times the concentration of the media. The accumulation was 1.7 times greater in the papilla than in the cortex and behaved as a saturable transport system. The papilla actively accumulated the above amino acids in media of increasing sodium concentrations up to 439 mequiv/l and in media made hyperosmolal with sucrose, whereas active accumulation of the amino acids in the renal cortex was absent or greatly diminished under these same experimental conditions. Slices of renal papilla also concentrated α aminoisobutyric acid and lysine in oxygen-deficient media. Aldosterone and vasopressin did not influence the amino acid uptake in the renal papilla or cortex. The results of this study indicate that the papilla is able to accumulate amino acids actively in vitro under conditions which simulate the environment of the papilla in vivo and which are detrimental to the accumulation of amino acids in the renal cortex. © 1968.