Ornithine uptake by isolated hepatocytes and distribution within the cell

Uptake of ornithine by isolated hepatocytes and its distribution within the cell was investigated. Ornithine uptake was energy independent and exhibited a saturable and a nonsaturable component. The Km value of the saturable component was 1.3 mM. At an external ornithine concentration of 0.5 mM the rate of ornithine uptake was 127 +/- 19 nmol/g. Lysine inhibited ornithine uptake, indicating the existence of an ornithine transport system. It was concluded that ornithine transport can limit urea synthesis in the state of transition from a low ammonia to a high ammonia supply.