Biosynthesis of Human Growth Hormone and Prolactin

Human pituitary glands were incubated with 3H-l,4,5-leucine in Krebs-Ringer bicarbonate buffer to study the biosynthesis and secretion of human pituitary proteins generally and growth hormone specifically. After 4 and 24 hr, anti-HGH serum precipitated only 3 and 13%, respectively, of the 3H-proteins in the medium. Following gel filtration of the medium on Sephadex, a single radioactive protein peak emerged with an elution volume which was not quite coincident with the elution volume of HGH and the protein peak. FSH, LH and TSH were present in earlier fractions and ACTH in later fractions. The total amount of all 4 hormones in the media was a thousandfold less than the amount of HGH in the media. Anti-HGH serum precipitated less than 5% of the 3H-proteins in the tubes which contained HGH, yet the latter accounted for more than 80% of the proteins in these fractions. Hence, the specific activity of the remaining proteins present in these fractions was very much greater than that of HGH. In the tis...