Insulin-like growth factors I and II and their binding proteins in human milk: effect of heat treatment on IGF and IGF binding protein stability.
Insulin-like growth factors (IGF-I and -II) are peptide growth factors that contribute to the growth-promoting properties of human milk. IGFs in extra cellular fluids are associated with high-affinity binding proteins (IGFBPs). In this study, IGF-I and -II, and IGFBPs in human milk were characterized, and the stability of the IGFs and IGFBPs to heat treatment was investigated. IGF-I and -II were quantified by radioimmunoassays of acid-chromatographed samples, and IGFBPs were characterized using Western ligand blotting. The concentration (mean +/- SD) of IGF-I in human milk was 1.5 +/- 0.5 micrograms/L, compared to 2.7 +/- 0.7 micrograms/L for IGF-II. Heat treatment did not significantly affect either IGF-I or -II content. Human milk contains a single, nonglycosylated, IGFBP, with an apparent Mr of 31 k, which was immunoprecititable by an antibody to IGFBP-2. Stability of the IGFBP to heat treatment was assessed and was not significantly affected by heat treatment. Therefore, both IGF-I and -II, and the IGFBP in human milk appear to be stable under heat treatment conditions routinely used for processing banked human milk.
Donovan
S M
SM
Department of Pediatrics, Stanford University Medical Center, California.
Hintz
R L
RL
Rosenfeld
R G
RG
D015153:Blotting, Western; D002352:Carrier Proteins / Q000032:analysis*; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006358:Hot Temperature; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D007335:Insulin-Like Growth Factor II / Q000032:analysis*; D008894:Milk Proteins / Q000032:analysis; D008895:Milk, Human / Q000737:chemistry*; D011233:Precipitin Tests
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D008894:Milk Proteins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II