Changes in Macromolecular Synthesis Associated with the Induction of Glutamine Synthetase in Embryonic Retina

Abstract

The hydrocortisone-mediated induction of glutamine synthetase in the neural retina of chicken embryo in vitro is correlated with enhanced incorporation into protein of [¹⁴C]aspartic acid, an amino acid abundant in this enzyme. In the induced retina labeled with [¹⁴C]aspartic acid, a peak of radioactivity was detected in the region of the polysomal profile corresponding to polysomes comprising 12-14 ribosomes. In retinas labeled with [³H]uridine, an increased amount of radioactivity was also detected in the same polysomal region of the hydrocortisone-induced retina. If we assume a monocistronic messenger RNA for retinal glutamine synthetase, this region corresponds to the estimated size of the polysomes necessary for the translation of this enzyme. The evidence presented demonstrates a correlation between these changes in incorporation and the induction of glutamine synthetase.