Characterization of adenohypophysial polypeptides by two-dimensional gel electrophoresis. I. L-[3H]leucine-labeled polypeptides.

Homogenates of cow and rat anterior pituitary slices, labeled in vitro with L-[3H]leucine, were analyzed by high-resolution two-dimensional polyacrylamide gel electrophoresis. This technique was also applied to the materials released into the chase medium from bovine anterior pituitary slices. The pattern of both total polypeptides (revealed by Coomassie-Blue staining) and L-[3H]leucine-labeled polypeptides (revealed by fluorography) was found to be more complex than previously demonstrated by different techniques. In particular, the GH band separated by one-dimensional Na-dodecylsulfate--polyacrylamide gel electrophoresis was resolved into 3--5 components; 2 of these, which were highly labeled by L-[3H]leucine, were both identified as GH by immunoprecipitation with specific anti-GH bodies. In addition, we found evidence in favor of the existence of some, previously unsuspected, 'putative' secretory proteins. In fact, besides GH and PRL, several minor components (2 with apparent Mr approximately 70 00--62 000, pI approximately 4.8; others with Mr approximately 50 000, pI between approximately 5.8 and approximately 6.8; and 1 with Mr approximately 26 000, pI approximately 5.7) were found to be synthesized at high rates and to accumulate in the medium, with different kinetics, during chase incubation.