Transport of methionine and proline by rat liver slices and the effect of certain hormones.

1. Transport characteristics of l-methionine and l-proline in rat liver slices in vitro were studied. 2. Intracellular concentration gradients for methionine were obtained. 3. Methionine uptake was inhibited by iodoacetate, dinitrophenol, Na(+)-free media and also by glycine, lysine, cysteine and dithiothreitol but not by alpha-aminoisobutyrate. 4. The rate of methionine metabolism in the slice was slow. 5. Puromycin inhibited methionine incorporation into protein, but not methionine uptake. 6. Methionine inhibited the transport of alpha-aminoisobutyrate but not of cystine. 7. Efflux and exchange diffusion of methionine was studied. 8. Amino acid transport in rat liver slices was not affected by thyroidectomy. 9. Addition of insulin, glucagon, adrenaline or cortisol did not affect the transport of methionine. 10. Addition of 6-N,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate increased methionine transport after a 120min incubation period in some experiments. 11. Studies of l-proline transport were invalidated because of the rapid evolution of CO(2) from the substrate.