Ornithine uptake by rat liver mitochondria: effect of calcium and arginine

The effect of calcium and L-arginine on ornithine uptake by rat liver mitochondria was studied. In the absence of arginine, calcium ions at a concentration of 0.36 microM increase ornithine uptake 218% above control, but at metal concentrations higher than 1.0 microM the amino acid uptake is diminished. Keeping calcium concentration constant in the medium (0.36 microM), ornithine transport was maximal at 5.0 microM L-arginine and decreased at higher concentrations of arginine. The possible role of calcium and arginine as physiological regulators of ornithine transport is discussed.