[Alanine transport in a mammalian cell culture]

The transport of L-alanine in cultured 3T3, 3T6 and CHO cells has been studied. The estimated Michaelis kinetic constants KM and Vmax for 3T3, 3T6 and CHO cells were 0.6 mM and 3 mM/min, 2.5 mM and 8.3. mM/min, 0.7 mM and 8.4 mM/min, respectively. Alanine transport was inhibited by glycine, serine, alpha-aminoisobutyric acid, methionine, and in a lesser degree by leucine and valine. Glycine depressed alanine transport with the constant of inhibition (Ki) similar to the constant of glycine transport (Km). Alanine transport was strictly diminished in a Na+-dependent medium at the expense of the increase of Km for transport. It is concluded that in 3T3, 3T6 and CHO cells, alanine is transported by the Na+-dependent "A" system.