Action of insulin on amino acid uptake by the immature rat uterus in vitro.

SUMMARY 1. The uptake of ~-aminoisobutyric acid by the immature rat uterus was studied kinetically in vitro, and the stimulatory action of inzulin on uptake was characterized. Other amino acids were also studied for comparison. 2. ~-Aminoisobutyric acid uptake was increased if the uteri were pretreated with insulin for 20 rain or more. The V of the saturable transport was increased by 19 ~ by insulin treatment, but no Kr, change was apparent. 3. Puromycin eliminated the insulin action on e-aminoisobutyric acid uptake within 40 min of treatment. 4. The effect of insulin on ~-aminoisobutyric acid uptake was abolished either by a preliminary 10-min incubation of the uterus with a high concentration (1 mM) of N-ethylmaleimide; or by incubation, concurrent or subsequent, with a low concentration of N-ethylmaleimide (0.05 mM). 5. The uptake of L-proline, L-methionine and glycine, but not that of L-leucine or L-valine, was also increased by insulin treatment. Insulin acted on a Na +-dependent uptake; it was without effect on the Na+-independent uptake of either e-aminoisobutyric acid or methionine. The evidence suggests that insulin acts on the A system of amino acid transport in the uterus.