Regulation of growth in cultured mammary epithelium from beef and
dairy heifers
T.B. McFadden, D.C. Cockrell
Dairying Research Corporation, Ruakura Agricultural Centre, Private
Bag, Hamilton, New Zealand
Proceedings of the New Zealand Society of Animal Production. 1993,
53: 143-146
Growth of mammary epithelium is regulated by endocrine signals, local
factors and sensitivity of epithelial cells to mitogens and inhibitors. This
study was designed to identify how these factors interact in regulating
mammogenesis and determine if breed differences exist among these factors.
Mammary epithelial cell organoids were isolated from five pairs of beef and
dairy heifers (7 to 9 months of age) and cultured within collagen gels. Sera
were collected from all heifers and pooled within breed for use in culture. At
slaughter, explants of mammary fat pad were also prepared for culture.
Culture treatments were arranged in a 2x2x3x4 factorial design. Factors
included source of cells (beef or dairy), addition of growth factors (10 ng/ml
IGF-I + 50 ng/ml EGF or control), source of mammary fat pad explants (beef,
dairy or none) and source of serum added to culture media at 5% final
concentration (beef, dairy, foetal calf serum, or none). Mammary growth was
assessed as incorporation of [3H]thymidine into DNA. Mammary epithelial
cells from beef heifers grew more rapidly than dairy cells (2518 vs 1192)
cpm/ug; P<0.01). Growth of epithelia was enhanced by addition of growth
factors (2265 vs 1445 cpm/ug; P<0.01). Sera from both beef and dairy
heifers stimulated growth 2-fold compared to no serum (P<0.01), but addition
of mammary fat inhibited epithelial growth (P<0.05). Cells from beef heifers
were also more responsive to addition of serum and growth factors. These
findings demonstrate that multiple factors interact to control mammary
growth. Mammary fat pad of ruminants, unlike rodents, appears to inhibit
epithelial growth.
Keywords: NZSAPAB;
Heifers; mammary; growth; breed.
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Last Updated 25-01-1997
