The insulin-like growth factor I content in human milk increases between early and full lactation.
The concentration of immunoreactive insulin-like growth factor I (IGF-I) in human mammary secretions, assayed after acid-ethanol extraction, was high [mean, 4.1 +/- 0.5 (+/- SE) nmol/L; n = 13] for several weeks prepartum. It then decreased during the first 3 days postpartum to 1.3 +/- 0.1 nmol/L (n = 28), in parallel with changes in epidermal growth factor (EGF) and protein concentrations. However, between the first and sixth weeks postpartum, the IGF-I concentration increased to 2.5 +/- 0.2 nmol/L (n = 18), while levels of EGF and protein decreased further. Given that the volume of milk produced increases during this period, the total IGF-I output rose by up to 4-fold, while EGF output remained constant. The increase in IGF-I and decrease in EGF in milk suggest that different regulatory mechanisms control the output of different growth factors by the mammary gland.
Corps
A N
AN
Agricultural and Food Research Council, Institute of Animal Physiology and Genetics Research, Babraham, Cambridge, United Kingdom.
Brown
K D
KD
Rees
L H
LH
Carr
J
J
Prosser
C G
CG
D004815:Epidermal Growth Factor / Q000032:analysis; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D007774:Lactation / Q000378:metabolism*; D008894:Milk Proteins / Q000032:analysis; D008895:Milk, Human / Q000032:analysis*; D049590:Postpartum Period / Q000378:metabolism; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D011863:Radioimmunoassay; D013002:Somatomedins / Q000032:analysis*; D013997:Time Factors
D008894:Milk Proteins; D013002:Somatomedins; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I