Purification, Characterization and Comparison of Immunological Properties of Monkey Chorionic Somatomammotropin with Human and Monkey Growth Hormone, Human Chorionic Somatomammotropin and Ovine Prolactin

Abstract

A method is presented which utilizes ammonium sulfate precipitation, pH and alcohol fractionation, and a final Sephadex G–100 chromatographic step for small scale purification of monkey chorionic somatomammotropin (mCS) from rhesus monkey placentae. Recoveries average 15 mg/kg placenta, one—sixth the estimated content. mCS appears to be a polypeptide of mol wt between 21,000 and 22,000, estimated by molecular sieving and dodecyl sodium sulphate polyacrylamide electrophoresis. It is highly acidic (pI 4.4) on electrofocusing and migrates more anodally than either human growth hormone (hGH) or human chorionic somatomammotropin (hCS) on electrophoresis at pH 9.5. mCS tends to polymerize irreversibly on storage in alkaline solution and to lose immunoreactivity. Immunological studies reveal greater similarity between mCS and hGH than mCS and hCS, and total dissimilarity with ovine prolactin (OP). This suggests that the structural configuration of mCS may provide information on the nature of the growth—promoting and lactogenic determinants on these molecules. A radioimmunoassay for mCS has been established in which human and monkey growth hormone and hCS react minimally and OP does not cross—react. Identical curves of displacement of labeled mCS from antisera to mCS by placental extracts and pregnant monkey plasma indicate that mCS is the material circulating in plasma of pregnant rhesus monkeys and is unaltered from mCS found in crude placental extracts. (Endocrinology92: 1051, 1973)