Determination of insulin-like growth factors in bovine milk and colostrum by radioimmunoassay
1998
Nikolic, J.A. | Masnikosa, R. (Institute for the Application of Nuclear Energy - INEP, Belgrade - Zemun (Yugoslavia))
The mean concentration of insulin-like growth factor-1 (IGF-1) and insulin-like growth factor-2 (IGF-2) colostrum were found to be 345 =- 200 ng/mL and 406 +- 46 ng/mL, respectively. When milk samples were centrifuged to remove the fat before radioimmunoassay, IGF-1 levels were found to be lower than in non-centrifuged samples, whereas no differences were detected concerning IGF-2 concentrations. This indicates that these growth factors are distributed differently in the milk emulsion. Thus, concentrations of IGF-1 decreased from 38 +- 3.5 ng/mL and 24.0 +- 2.8 ng/mL at four days postpartum to 7.2 +- 6.6 ng/mL and 4.1 +- 3.7 ng/mL in whole and centrifuged mature milk samples, respectively. Mean IGF-2 concentrations were 14.1 +- 6.0 ng/mL and 13.7 +- 6.1 ng/mL in whole and centrifuged milk samples, respectively. Pasteurized milk contained lower concentrations of both factors (IGF-1 - 1.1 +- 0.9 ng/mL; IGF-2 - 6.5 +- 3.2 ng.mL). Even lower amounts, near or below the limit of the sensitivity of the assay systems (1 ng/mL) were found for humanised milk powders intended for human infants.
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