Modification by Insulin of the Distribution of Two Model Amino Acids in the Rat1

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Abstract
Results are reported from a study of the effect of insulin on the distribution in rats of previously injected doses of the model amino acids, 1-aminocyclopentanecarboxylic acid and [alpha] -aminoisobutyric acid. All studies were made 24 or 39 hr. after giving amino acid. Injection of 2 U of the hormone per kg of body weight per rat resulted in increased2 distribution ratios of both amino acids in liver, heart, diaphragm and skeletal muscle after 2 hr. The effects were less after 1/2 hr and also when 0.2 U/kg was used for 2 hr. in general, the effects were greater with 1-amino-cyclo-pentanecarboxylic acid than with [alpha]-aminoisobutyric acid. The results suggest that the increased distribution ratios of the 2 amino acids produced in the 3 muscle tissues were predominantly a result of a direct action of the hormon?. Liver showed the largest increase in uptake ot 1-aminocyclopentanecarboxylic acid after insulin injection (as much as a 5-fold elevation when 2 U insulin/kg was given). Close examination of this stimulation led to the conclusion that most of the effect was due to the action of other hormones released either directly or indirectly in response to the insulin hypoglycemia. Only a small part of the effect (about 10-20%) could be attributed to a direct action of insulin to cause elevated transfer of the amino acid into the liver.