Purification from human pregnancy serum of a low molecular weight mitogen similar to placental lactogen and growth hormone.
Recently, we isolated from the serum of pregnant women a factor that induced rapid proliferation of a lactogen-dependent rat lymphoma cell line (Nb2). This mitogenic factor is reasonably specific to pregnancy, since it was present in serum samples from second trimester as well as term-pregnant women, but not in those of adult men or cycling females. It is unlikely that this mitogenic activity (referred to as pregnancy mitogen [PM]) is due to contamination by classical lactogens, since acetone fractionation of serum yielded a preparation devoid of placental lactogen and prolactin, as determined by radioimmunoassays. Further purification of acetone precipitates from term-pregnant serum by ion exchange chromatography and gel filtration yielded a mitogenic activity with a relative mol wt of approximately 10,000. PM activity in the NB2 cell bioassay was not affected by the presence of prolactin antiserum. However, its activity was immunoneutralized by coincubation with anti-placental lactogen serum and, to a lesser extent, anti-growth hormone serum. It appears that PM was not generated by our extraction procedure, since gel filtration of whole serum also yielded a bioactive fraction of approximately 10 kDa. PM was further purified to homogeneity by high-performance liquid chromatography. Examination of the preliminary amino acid composition of PM revealed differences from that of a bioactive fragment of growth hormone and a corresponding portion of placental lactogen, suggesting that PM could be either a molecular variant of these hormones or a novel protein.
Kineman
R D
RD
Department of Anatomy and Cell Biology, Medical University of South Carolina, Charleston 29425.
Büllesbach
E E
EE
Schwabe
C
C
Boggs
K P
KP
Frawley
L S
LS
D000596:Amino Acids / Q000032:analysis; D001681:Biological Assay; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D005260:Female; D013006:Growth Hormone / Q000737:chemistry; D006133:Growth Substances / Q000097:blood* / Q000737:chemistry; D006801:Humans; D009500:Neutralization Tests; D010928:Placental Lactogen / Q000737:chemistry; D011247:Pregnancy / Q000097:blood*; D011863:Radioimmunoassay; D014407:Tumor Cells, Cultured
D000596:Amino Acids; D006133:Growth Substances; D013006:Growth Hormone; D010928:Placental Lactogen