Purification of a Placental Factor with Immunological and Chemical Similarity to Human Growth Hormone11

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Abstract
Finely powdered frozen placental tissue was extracted at pH 8.0, and the pH 4.5 soluble portion was precipitated with half-saturated ammonium sulfate at pH 5.6. This was extracted with 0.1M ammonium bicarbonate and fractionated on columns of Sephadex G-100 using 0.1M ammonium bicarbonate as the buffer. Most of the active principle was contained in a minor fraction of the more retarded components, and on starch gel electrophoresis this showed one major band which on immunoelectrophoresis cross-reacted with antiserum to human growth hormone. The same substance, present in large concentration, has been identified in and purified from retroplacental blood. Upon starch gel electrophoresis, human growth hormone and the placental protein have different mobilities, but their molecular weights and amino acid compositions are very similar. Some, but not all, preparations of the purified placental extract stimulated growth in hypophysectomized rats. The substance with the growth-promoting activity was in the same segment as the placental protein after starch gel electrophoresis. Other biological effects observed after an injection of the placental protein into rats included an increase in serum ketone bodies without a concomitant increase in serum free fatty acids and a slight decrease in the concentration of glucose. The placental protein had no effect on the release of free fatty acids from isolated rat adipose tissue, but, like human growth hormone, it stimulated the uptake of Uglucose- l4C, its oxidation to CO2 and its conversion into fat in vitro. (Endocrinology76: 369, 1965)