The distribution and biosynthesis of the polypeptides of the hypothalamo-neuropypophyseal complex

Proteins of the posterior lobe, lower, middle and upper stalk and hypothalamus were compared after starch gel electrophoresis. In each species several proteins which were present in the posterior lobe were also found in the stalk but in decreasing amounts in its upper part. Some proteins were undetectable in the hypothalamus but present in the stalk including peptides II and III, which bind vasopressin. Protein synthesis in each of the regions was studied with 3H-I-leucine. The greatest incorporation of radioactivity occurred in the upper and middle stalk, which was twice that of the anterior lobe, while that of the posterior lobe and hypothalamus was one hundredfold less. After incubation the proteins were separated by gel filtration and electrophoresis. One component, named peptide IV, which was present in each region contained more radioactivity than either peptide II or III. The neurohypophyseal complex and especially the stalk median eminence region is the site of very active synthesis including some of the posterior lobe proteins