An apparent inhibition of insulin biosynthesis resulting from inhibition of transport of neutral amino acids by arginine.

At concentrations higher than 10 mM, the cationic amino acid, arginine, inhibited the incorporation of neutral amino acids such as alanine, threonine, valine and leucine into insulin in the presence of glucose. This inhibitory effect probably did not result from the stimulatory effect of argnine on insulin release because, in the absence of glucose, arginine failed to stimulate insulin release but nevertheless inhibited the incorporation of leucine into insulin. This inhibitory effect of arginine was shared by another basic amino acid, histidine, but not by lysine. Arginine inhibited the incorporation of leucine not only into insulin but also into other islet proteins. This inhibition was not accompanied by any disturbance of glucose metabolism in the islet cells. Further studies indicated that the inhibition of incorporation resulted primarily from the interference of uptake of the neutral amino acids by arginine.