Insulin action in pancreatic acini from streptozotocin-treated rats. I. Stimulation of protein synthesis.

Pancreatic acini were prepared from rats rendered diabetic with streptozotocin. In this tissue, insulin stimulated [3H]leucine incorporation into protein. The full effects of insulin on this function were not immediate but increased linearly with time for up to 2 h of incubation. Insulin had a detectable effect on l eucine incorporation at 50 pM, a half-maximal effect at 0.7 nM, and a maximal effect at 30 nM. Desdipeptide proinsulin was only 10% as potent as native insulin in stimulating [3H]leucine incorporation, whereas proinsulin and desoctapeptide insulin were only 1% as potent. Insulin also increased the incorporation of [3H]valine and [35S]methionine into protein but did not increase the influx of either [14C]cycloleucine or alpha-[3H]aminoisobutyric acid. These observations suggested that the increased incorporation of labeled amino acid into protein reflected stimulation of protein synthesis rather than stimulation of amino acid transport. Furthermore, insulin at 1.67 nM significantly increased the acinar cell concentration of amylase. The present findings are consistent therefore with the concept that insulin regulates pancreatic exocrine functions, including protein and enzyme synthesis.