The effect of calcium on mammary epithelial cell proliferation and the plasminogen activating system

The objectives of this study were to examine 1) the effect of extracellular calcium on proliferation of bovine mammary epithelial cells, 2) whether extracellular calcium regulates the mitogenic effect of insulin-like growth factor (IGF-I) and epidermal growth factor (EGF) towards mammary epithelial cells, and 3) whether the effects of calcium on growth are mediated through changes in the plasminogen activating system. The BME-UV1 cells were used as a model system. Results showed that optimal proliferation of BME-UV1 cells grown in the presence of 10% dialyzed FBCS was achieved when the culture medium was supplemented with 1–2 mmol L−1 of extracellular Ca2+. IGF-I (P<0.01) but not EGF, increased proliferation of BME-UV1 cells. Furthermore, calcium does not regulate IGF-I and EGF responsiveness of BME-UV1 cells. Northern blot analysis was performed to examine the effect of extracellular calcium on expression of urokinase-type plasminogen activator (u-PA), PA inhibitor 1 (PAI-1) and u-PA receptor (u-PAR) genes by BME-UV1 cells in culture. Results showed that calcium increased expression of all above-mentioned genes after 24 h of exposure of cells to calcium, at a time that the effect of calcium on growth was not apparent. Calcium had no effect on u-PA and u-PAR expression after 48 and 72 h of exposure of cells to calcium, at a time that the effect of calcium on growth was predominant. Calcium caused a small increase of PAI-1 expression after 48 and 72 h but this small increase is apparently of limited biological value. Key words: Mammary epithelial cells, calcium, growth factors, plasminogen activating system

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Differential effects of retinoids on proliferation of bovine mammary epithelial cells in collagen gel culture

Journal of Dairy Research ◽

10.1017/s0022029901004782 ◽

2001 ◽

Vol 68 (2) ◽

pp. 157-164 ◽

Cited By ~ 16

Author(s):

STIG PURUP ◽

SØREN KROGH JENSEN ◽

KRIS SEJRSEN

Keyword(s):

Cell Proliferation ◽

Retinoic Acid ◽

Growth Factors ◽

Growth Factor ◽

Epithelial Cells ◽

Mammary Epithelial Cells ◽

Collagen Gel ◽

Mammary Epithelial ◽

Bovine Mammary Epithelial Cells ◽

Igf I

The effects of increasing concentrations of retinol, retinal and retinoic acid on proliferation of bovine mammary epithelial cells were investigated in collagen gel cultures. All retinoids significantly inhibited proliferation of mammary epithelial cells. The relative inhibitory potency of the retinoids was: retinoic acid > retinal > retinol. Maximal inhibition at 10 μg/ml corresponded to a 75–95% inhibition of proliferation obtained in basal medium. Retinol, retinal and retinoic acid also inhibited proliferation of cells growth-stimulated with insulin-like growth factor-I (IGF-I). Retinoids in highest concentrations (10 μg/ml) inhibited 68–85% of proliferation of cells obtained in culture medium containing 25 ng IGF-I/ml. Retinol and retinoic acid also inhibited proliferation of cells growth-stimulated by insulin and other growth factors from the IGF growth factor family (des(1-3)IGF-I and IGF-II), as well as growth factors from the epidermal growth factor family (EGF and TGF-α), with retinoic acid being more effective than retinol. At a concentration of 100 ng/ml, retinol and retinoic acid inhibited respectively 24–38 and 44–52% of mammary cell proliferation stimulated by growth factors of the IGF family, and at 10000 ng/ml, 61–71% of cell proliferation was inhibited. The growth-stimulating effect of insulin, EGF and TGF-α was inhibited 42–64% by retinol and retinoic acid at 100 ng/ml, and 64–84% at 10000 ng/ml. The present results show that retinol, retinal and retinoic acid are potent inhibitors of bovine mammary epithelial cell proliferation. It is suggested that retinoids may have concentration-dependent roles in regulation of pubertal mammary growth and development, indicating that the milk yield potential of heifers may be affected by vitamin A status.

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