Stimulatory effect of insulin-like growth factor-I on [3H]thymidine incorporation, DNA content and insulin biosynthesis and secretion of isolated pancreatic rat islets.

The influence of insulin-like growth factor-I (IGF-I) on both the growth and function of isolated pancreatic rat islets was studied. As a measure of islet cell replication, [3H]thymidine incorporation and DNA content was estimated at the same time as parameters for (pro)insulin biosynthesis and secretion as a measure of the functional capacity of B cells. Incorporation of [3H]thymidine was measured after tissue solubilization; DNA was determined fluorometrically. (Pro-)insulin biosynthesis was determined by incorporation of [3H]leucine after immunoprecipitation and binding to protein A-Sepharose. There was a significant increase in both [3H]thymidine incorporation and DNA content after the culture of islets with IGF-I. IGF-I resulted also in an increase in insulin biosynthesis and secretion from isolated pancreatic islets. These results demonstrate a role of IGF-I in regulating the growth and function of pancreatic islets.