Purification and assay of insulin-like growth factor-binding protein-1: measurement of circulating levels throughout pregnancy

in Journal of Endocrinology
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H. S. Wang
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L. A. Perry
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J. Kanisius
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R. K. Iles
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J. M. P. Holly
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T. Chard
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ABSTRACT

Insulin-like growth factor-binding protein-1 (IGFBP-1) has been purified from amniotic fluid by anion exchange, hydrophobic interaction and gel filtration chromatography. The overall recovery of the purification process was 12·2%. The purified IGFBP-1 yielded a single band on SDS-PAGE gel but showed two bands (34 kDa and 68 kDa) on Western blot under non-reducing conditions. Polyclonal antisera were raised by immunization of sheep using the purified IGFBP-1. The best antiserum bound 50% of 125I-labelled IGFBP-1 at a final dilution of 1:500 000. A radioimmunoassay for IGFBP-1 was developed. This assay had a minimum detection limit of 5 μg/1, and was used to determine serum levels in non-pregnant and pregnant women. There was no cross-reaction with a wide variety of materials tested. Serum IGFBP-1 levels in non-pregnant individuals (33±16 (s.D.) μg/1) were found to be significantly lower than those in the second (96±64 μg/1) and third trimesters (95 ±60 μg/1) of pregnant women. During pregnancy, circulating IGFBP-1 levels increased rapidly in the first trimester and reached a peak at 12–13 weeks of gestation (107±75 μg/l). The level then remained at 80±53 to 103±70 μg/l until term.

Journal of Endocrinology (1991) 128, 161–168

 

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