Different effects of growth hormone on growth and function of isolated adult and fetal rat pancreatic islets.

We simultaneously determined 3H-thymidine incorporation, DNA content, and insulin biosynthesis in adult and fetal rat pancreatic islets. 3H-thymidine incorporation was measured after tissue solubilization. DNA was measured fluorometrically. Insulin biosynthesis was determined through 3H-leucine incorporation after immunoprecipitation and binding to protein A-sepharose. Addition of growth hormone caused a significant increase in 3H-thymidine incorporation into both the adult and the fetal islets, but only the adult islets experienced an increase in DNA content. The increase in 3H-leucine incorporation was also significant only in the adult islets. The dynamics of 3H-thymidine incorporation after growth hormone administration were different in the adult and the fetal pancreas. Fetal islets have the potential to increase their incorporation of 3H-thymidine, but very limited potential for insulin biosynthesis.