IMMUNOBLOT STUDIES OF THE ACID-LABILE SUBUNIT (ALS) IN BIOLOGICAL-FLUIDS, NORMAL HUMAN SERUM AND IN CHILDREN WITH GH DEFICIENCY AND GH RECEPTOR DEFICIENCY BEFORE AND AFTER LONG-TERM THERAPY WITH GH OR IGF-I RESPECTIVELY

Citation
Ji. Labarta et al., IMMUNOBLOT STUDIES OF THE ACID-LABILE SUBUNIT (ALS) IN BIOLOGICAL-FLUIDS, NORMAL HUMAN SERUM AND IN CHILDREN WITH GH DEFICIENCY AND GH RECEPTOR DEFICIENCY BEFORE AND AFTER LONG-TERM THERAPY WITH GH OR IGF-I RESPECTIVELY, Clinical endocrinology, 47(6), 1997, pp. 657-666
Citations number
52
Categorie Soggetti
Endocrynology & Metabolism
Journal title
ISSN journal
03000664
Volume
47
Issue
6
Year of publication
1997
Pages
657 - 666
Database
ISI
SICI code
0300-0664(1997)47:6<657:ISOTAS>2.0.ZU;2-H
Abstract
OBJECTIVE The aims of this investigation were (a) to study the presenc e of immunoreactive forms of the acid-labile subunit (ALS) in differen t human biological fluids, (b) to define the age dependence of serum A LS in normal children and adults and (c) to compare the regulation of ALS by GH or IGF-I in children with GH deficiency (GHD) and GH recepto r deficiency (GHRD) before and after 1 year of therapy with GH or IGF- I, respectively. DESIGN AND PATIENTS Selected human biological fluids from different consenting volunteers and serum from 68 normal children and 5 adults were analysed. Four children diagnosed as GHD and 7 chil dren diagnosed as GHRD were treated with recombinant human (rh) GH at a dosage of 0.05 mg/kg/day s.c. or rhIGF-I at a dosage of 120 mu g/kg twice daily s.c., respectively, for 12 months. MEASUREMENTS Immunoreac tive forms of ALS were studied by Western immunoblot using a specific rabbit antiserum derived against synthetic human ALS and quantified by laser densitometry analysis. Serum from children with GHD or GHRD wer e sampled before and at 6 and 12 months of therapy; serum from these p atients had been also assayed at baseline for determination of IGF-I a nd IGF binding protein (IGFBP)-3 by radioimmunoassay and immunoradiome tric assay, respectively.RESULTS An immunoreactive 85 kDa doublet of A LS was detected in serum, plasma, follicular, peritoneal and synovial fluid, but not in urine, seminal plasma, amniotic or extra-embryonic c oelomic fluids. Assessment of serum from newborns to adults revealed a n age dependence; the ALS doublet was low, but detectable, in newborns , increased during adolescence and remained constant in adulthood. ALS levels were significantly lower in GHD (P=0.02) and in GHRD children (P=0.001) than in age-matched controls. Treatment with rhGH in GHD chi ldren produced a 2.7-fold increase in serum ALS concentrations at 6 mo nths of therapy (P=0.01), which was maintained after I year of treatme nt (P=0.006), leading to normalization of ALS concentrations. In contr ast, administration of rhIGF-I to GHRD children failed to increase and normalize serum ALS levels either at 6 or 12 months of therapy. CONCL USIONS Immunoreactive forms of acid-labile subunit are present in seru m and plasma, as well as in follicular, peritoneal and synovial fluids , suggesting that acid-labile subunit can either cross the capillary b arrier or be secreted locally. Acid-labile subunit concentrations are age-dependent with a sharp increase during adolescence, and are reduce d in GH deficient and GH receptor deficient children. While treatment with rhGH is able to increase and normalize acid-labile subunit concen trations in GH deficient children, therapy with rhIGF-I fails to incre ase serum acid-labile subunit levels in GH receptor deficient patients . These data suggest that acid-labile subunit is directly GH-regulated , and that IGF-I cannot increase acid-labile subunit levels, as assess ed by Western immunoblot.