Studies of the kinetics of amino acid transport, incorporation into protein and oxidation in kidney-cortex slices

Abstract

The present report describes an approach to the study of the steady-state kinetics of amino acid transport and protein synthesis in rat-kidney-cortex slices, using multi-compartment models. The following conclusions seem justified from the data presented: 1.1. Using inulin and the non-metabolizable amino acid, α-aminoisobutyric acid, amino acid uptake could be characterized by a three-compartment “parallel” model representing the medium, extracellular space and intracellular space. Appropriate influx and efflux rate constants were calculated.2.2. 2,4-Dinitrophenol and incubation at 27° significantly effected the rate of efflux of α-aminoisobutyric acid from the intracellular space, as well as the rate of influx, suggesting that efflux phenomena are metabolically linked.3.3. Kinetic studies of combined transport and protein synthesis with glycine and l-lysine indicated that equilibration of exogenous amino acid with the intracellular pool need not occur before incorporation into protein takes place.4.4. The kinetics of 14CO2 evolution from labeled l-lysine indicated that the rate of amino acid oxidation reflected the buildup of the intracellular lysine pool.5.5. The results suggest that the mathematical approach, used in the analysis of the experimental data, provides means of quantitating and understanding membrane phenomena and the relationship between rates of membrane transfer and subsequent intracellular utilization.