tretinoin and 2-aminoisobutyric-acid

The effect of retinoic acid (RA) on the uptake and utilization of extracellular amino acids by fetal lung fibroblasts was examined. RA decreased the incorporation of [3H]proline into collagen and other proteins. The effect was maximal at a RA concentration of 10(-5) M; smaller decreases were observed at a RA concentration of 10(-6) M. This decrease in collagen formation was associated with a large decrease in intracellular [3H] proline. The decrease in intracellular [3H]proline was first observed at 2 h following the addition of RA to cell cultures. Transport studies employing radiolabeled amino acids revealed that RA decreased the uptake of proline, 2-aminoisobutyric acid, and 2-(methylamino)isobutyric acid but not leucine or methionine. Kinetic analysis of 2-aminoisobutyric acid uptake indicated that this effect was mediated primarily by an increase in apparent Km, with a lesser decrease in Vmax, RA-induced inhibition of proline uptake was not abolished by the presence of cycloheximide nor by pretreatment with indomethacin. Na+,K(+)-ATPase activity was not affected by RA treatment. These results suggest that RA modulates protein production in fibroblasts by altering the function of the Na(+)-dependent A transport system for amino acid uptake.

Topics: Amino Acids; Aminoisobutyric Acids; Biological Transport; Cycloheximide; Fibroblasts; Humans; In Vitro Techniques; Indomethacin; Leucine; Lung; Proline; Protein Biosynthesis; Tretinoin