Demonstration of insulin-specific mRNA in cultured rat retinal glial cells.

A number of studies have recently demonstrated that insulin may be synthesized outside the pancreas. The present study was designed to investigate whether insulin-like activity exists in retinal glial cells and if so, whether it is due to local synthesis of insulin. Immunocytochemical techniques using insulin antisera were applied to cultured rat retinal glial cells, and insulin-like immunoreactivity was demonstrated in the cytoplasm of these cells. In situ DNA-RNA hybridization studies using 3H-labeled rat insulin cDNA indicated that the glial cells, particularly the Müller cells of the retina also contained the mRNA necessary for de novo synthesis of insulin or a closely homologous peptide. This peptide may be important in neuromodulation or regulation of metabolism of retinal cells and capillaries.