Characterization of insulin-like growth factors and their binding proteins in peritoneal dialysate |
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Authors: | Arundhati S Kale Frances Liu Raymond L Hintz Bonita K Baker Eileen D Brewer Phillip D K Lee Susan K Durham David R Powell |
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Institution: | (1) Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA, US;(2) Department of Pediatrics, Stanford University Medical Center, Stanford, California, USA, US;(3) Diagnostic Systems Laboratories, Webster, Texas, USA, US |
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Abstract: | .Serum insulin-like growth factors (IGFs), which circulate bound to specific IGF binding proteins (IGFBPs), must exit the
intravascular space before acting on target tissues. Little is known about the nature of IGF/IGFBPs in extravascular fluids
of patients with chronic renal failure (CRF). Peritoneal dialysate (PD) was studied since, after a short incubation, PD contains
proteins which have entered an extravascular space; thus, IGF/IGFBP forms in PD are more likely than serum forms to interact
with target tissues. IGF-I and IGF-II, and IGFBPs 1 – 4, were readily identified by specific immunoassays and/or 125iodine-IGF ligand blotting of simultaneously obtained PD and serum samples from seven CRF children; IGFBP-3 was a major IGFBP
in PD as in serum. Where quantitated, IGF and IGFBP levels in PD were approximately 10% of serum concentrations. After separation
of PD and serum by size-exclusion chromatography, serum had more IGFBP-3 in 150-kilodalton (kDa) than 35-kDa fractions, while
PD had far less IGFBP-3 in 150-kDa than 35-kDa fractions. Immunoblot studies revealed a major 29-kDa IGFBP-3 fragment, in
addition to intact 41- and 38-kDa IGFBP-3 forms, in PD and CRF serum; the 29-kDa form predominated in the 35-kDa PD fractions.
These data suggest that the 29-kDa fragment is the IGFBP-3 form most likely to modulate IGF effects on target tissues of CRF
individuals.
Received: April 17, 1995; received in revised form September 19, 1995; accepted October 12, 1995 |
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Keywords: | : Insulin-like growth factor Insulin-like growth factor binding protein Chronic renal failure Peritoneal dialysate |
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