Measurement of human IGF-II using Sephacryl extraction: a rapid and reliable assay method.
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 micrograms/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.
Mason
B H
BH
Department of Endocrinology, Auckland Hospital, New Zealand.
Tatnell
M A
MA
Holdaway
I M
IM
D000180:Acrylic Resins; D000328:Adult; D000368:Aged; D002850:Chromatography, Gel; D003911:Dextrans; D005260:Female; D005782:Gels; D006801:Humans; D007003:Hypoglycemia / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000302:isolation & purification; D007335:Insulin-Like Growth Factor II / Q000302:isolation & purification*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013997:Time Factors
D000180:Acrylic Resins; D003911:Dextrans; D005782:Gels; D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; C025614:sephadex