Modulation of mammary gland development in pre-pubertal mice as affected by soya and milk protein supplements

Abstract

The objective of the present study was to determine the effects of soya and whey milk protein, ±-lactalbumin (±-LA), on mammary gland morphology and the structural support of the gland, in pre-pubertal mice after 7 d of treatment. In Expt 1, weaned (day 21) CD1 mice were given one of the four treatments, three included dietary supplements: (1) control diet, casein, (2) soya, (3) ±-LA and (4) subcutaneous injection of 2•5 oestradiol benzoate in 20 Î1/4l maize oil and fed the control diet. All diets ere isoenergetic ith equal protein concentrations. All groups that ere not treated ith oestradiol received the vehicle. hole-mount analyses ere performed to determine longitudinal ductal gro th and terminal end bud development. DNA as extracted from the gland and assessed by spectrophotometry (260/280 nm). Tissue extracts for extracellular matrix (ECM) proteins, matrix metalloproteinase-2 (MMP2), tissue inhibitor of MMP2 (TIMP2), and serum oestradiol and mammary tissue epidermal gro th factors (EGF) ere measured by immunoassays. Expt 2 utilised the Her2/neu transgenic strain, ith the same protocols. Statistical significance as determined by one-ay ANOVA. From Expt 1 and 2, soya and ±-LA significantly increased ductal elongation hen compared ith the oestrogen and control groups. These results ere corroborated by data on total DNA and the ratio of MMP2:TIMP2. The ratio of MMP2:TIMP2 as affected by ±-LA. Serum oestradiol as decreased only in the oestradiol-treated groups in both experiments. Soya is kno n to be oestrogenic and can act on epithelia directly. The mechanism by hich ±-LA affects glandular development is by modulating the ECM or by promoting the synthesis/activity of EGF. © 2011 The Authors.