Free insulin‐like growth factors (IGF‐I and IGF‐II) in human serum

FEBS Letters - Tập 348 - Trang 185-191 - 1994
Jan Frystyk1, Christian Skjærbæk1, Bo Dinesen2, Hans Ørskov1
1Institute of Experimental Clinical Research, Medical Research Laboratories, Aarhus University Hospital, Nørrebrogade 44, DK-8000 Aarhus, Denmark
2Steno Diabetes Center, Gentofte, Denmark

Tóm tắt

Using ultrafiltration by centrifugation we have isolated the free, unbound fractions of insulin‐like growth factor I and II (free IGF‐I and IGF‐II) in human serum. In this way near in vivo conditions could be maintained before and during isolation. The recovery was 80 to 100% in the ultrafiltrates, which contained no detectable amounts of IGF‐binding proteins (IGFBPs) as measured by Western ligand blotting and IGFBP‐1 and IGFBP‐3 immunoassays. The concentration of free peptides was measured in two ultrasensitive non‐competitive IGF‐I and IGF‐II time‐resolved fluoroimmunoassays. We found that (i) equilibrium between free and protein‐complexed IGF was strongly dependent on re‐establishment of in vivo conditions (temperature, pH, ionic milieu and dilution); (ii) metabolic events (glucose load and fasting) caused significant changes in free IGF‐I and IGF‐II levels without concomitant changes in total circulating levels of IGFs; (iii) in 49 healthy adult subjects (20 to above 60 years) free IGF‐I was inversely related to age and ranged from 950 ± 150 ng/l (mean ± S.E.M.) (20–30 years) to 410 ± 70 ng/l (⪢ 60 years). The relative percentage was, however, unchanged, being 0.38 ± 0.02% of total IGF‐I. In contrast, free IGF‐II was independent of age, being 1,480 ± 80 ng/l (∼0.20 ± 0.01% of total IGF‐II).

Tài liệu tham khảo

1993 John Wiley and Sons Chichester New York J.M.P. Holly A. Flyvbjerg H. Ørskov K.G.M.M. Alberti Growth Hormone and Insulin-Like Growth Factor I in Human and Experimental Diabetes 47 76 10.1210/jcem-55-5-916 10.1172/JCI115796 10.1056/NEJM198707163170303 10.1530/acta.0.1210753 10.1172/JCI112500 10.1210/jcem-56-2-376 10.1172/JCI116480 10.1210/jc.75.1.30 Boulware S.D., 1992, Am. J. Physiol., 262, E130 10.2337/diab.40.8.959 Hizuka N., 1991, Growth Regul., 1, 51 Diagnostic System Laboratories Inc. Webster TX USA. Immunoradiometric kit for the quantitative measurement of free human IGF-I in serum or plasma. Hasegawa Y., 1994, Growth Regul., 4, II346 Frystyk J., 1994, Growth Regul., 4, II344 10.1210/jcem-51-4-781 10.1016/0003-2697(86)90507-5 10.1007/BF00400489 10.1093/clinchem/39.4.578 10.1093/clinchem/32.4.637 10.3109/00365517509095735 10.3109/00365517909104939 10.1002/jps.2600700208 10.1210/jcem-66-5-1014 10.1111/j.1651-2227.1991.tb17983.x
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FEBS Letters

Tập 348

185-191

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