Serum concentrations of free and total insulin-like growth factor-I, IGF binding proteins -1 and-3 and IGFBP-3 protease activity in boys with normal or precocious puberty

ABSTRACT Insulin-like growth factor-I (IGF-I), IGF-II and IGF-binding proteins (IGFBP) were examined in rat serum during pregnancy and lactation. IGF-I concentrations determined after acid column chromatography of serum were low during the last third of pregnancy. IGF-II was undetectable in pregnant and non-pregnant rats. IGF-binding protein (IGFBP) concentrations, measured as high molecular mass activity in the IGF-I RIA and the IGF-II RRA of acid column fractions, paralleled the changes observed with IGF-I. Western ligand blot analysis of serum from non-pregnant rats revealed a 40–50 kDa IGFBP aligning with IGFBP-3, a smaller 28–30 kDa doublet and 24 kDa IGFBP. Serum from rats in late pregnancy lacked IGFBP-3, whereas the smaller IGFBP persisted during late pregnancy. IGFBP-3 reappeared in postpartum animals. The fall in serum IGF-I is consistent with a maternal catabolic state during late pregnancy which may maximize substrate availability for the developing fetus. Journal of Endocrinology (1990) 127, 383–390

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Measurement of Human Igf-II Using Sephacryl Extraction: A Rapid and Reliable Assay Method

Annals of Clinical Biochemistry International Journal of Laboratory Medicine ◽

10.1177/000456329603300305 ◽

1996 ◽

Vol 33 (3) ◽

pp. 201-208 ◽

Cited By ~ 4

Author(s):

Barbara H Mason ◽

Michele A Tatnell ◽

Ian M Holdaway

Keyword(s):

Growth Factor ◽

Binding Proteins ◽

Complete Removal ◽

Assay Method ◽

Insulin Like Growth Factor ◽

Serum Concentrations ◽

Igf Binding Proteins ◽

Factor Ii ◽

Igf I ◽

Igfbp 3

Measurement of insulin-like growth factor II (IGF-II) in human serum is complicated by the presence of IGF binding proteins and usually involves cumbersome extraction procedures followed by radioimmunoassay. We have utilized an extraction process developed for measuring insulin-like growth factor II in ovine serum using Sephacryl HR100, and have applied this to the extraction of human samples followed by radioimmunoassay for human IGF-II. The assay yielded 98% recovery of unlabelled IGF-II, parallelism between dilutions of eluate and the standard curve, complete removal of binding proteins and near-complete removal of IGF-I, and intra- and interassay coefficients of variation of 5% and 9%, respectively. The normal range for serum IGF-II in women was 490–1056 μg/L, and IGF-II levels were positively correlated with serum concentrations of insulin-like growth factor binding protein-3 (IGFBP-3) but not with IGF-I levels. Mean serum concentrations of IGF-II were reduced below normal in a number of hypopituitary patients and children with short stature and IGF-II concentrations in these subjects correlated positively with IGF-I and IGFBP-3. In acromegalic patients IGF-II levels were usually normal and were negatively correlated with IGF-I concentrations. From our experience with the above results the present assay appears particularly suitable for clinical measurements and research projects where high sample throughput is required.

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