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Calcium transport by mammary secretory cells: mechanisms underlying transepithelial movement

100%

Shennan D. B.

Cellular and Molecular Biology Letters

2008

tom 13

nr 4

514-525

The secretion of calcium into milk by mammary epithelial cells is a fundamentally important process. Despite this, the mechanisms which underlie the movement of calcium across the lactating mammary gland are still poorly understood. There are, however, two models which describe the handling of calcium by mammary epithelial cells. On the one hand, a model which has existed for several decades, suggests that the vast majority of calcium enters milk via the Golgi secretory vesicle route. On the other hand, a new model has recently been proposed which implies that the active transport of calcium across the apical membrane of mammary secretory cells is central to milk calcium secretion. This short review examines the strengths and weaknesses of both models and suggests some experiments which could add to our understanding of mammary calcium transport.

Estrogen regulation and ion dependence of taurine uptake by MCF-7 human breast cancer cells

63%

Shennan D. B., Thomson J.

Cellular and Molecular Biology Letters

2007

tom 12

nr 3

It has been reported that estrogen receptor-positive MCF-7 cells express TauT, a Na+-dependent taurine transporter. However, there is a paucity of information relating to the characteristics of taurine transport in this human breast cancer cell line. Therefore, we have examined the characteristics and regulation of taurine uptake by MCF-7 cells. Taurine uptake by MCF-7 cells showed an absolute dependence upon extracellular Na+. Although taurine uptake was reduced in Cl- free medium a significant portion of taurine uptake persisted in the presence of NO3 -. Taurine uptake by MCF-7 cells was inhibited by extracellular β-alanine but not by L-alanine or L-leucine. 17β-estadiol increased taurine uptake by MCF-7 cells: the Vmax of influx was increased without affecting the Km. The effect of 17β-estradiol on taurine uptake by MCF-7 cells was dependent upon the presence of extracellular Na+. In contrast, 17β-estradiol had no significant effect on the kinetic parameters of taurine uptake by estrogen receptor-negative MDA-MB-231 cells. It appears that estrogen regulates taurine uptake by MCF-7 cells via TauT. In addition, Na+-dependent taurine uptake may not be strictly dependent upon extracellular Cl-.

Ograniczanie wyników

2 Cellular and Molecular Biology Letters

2 Shennan D. B.

1 Thomson J.

1 2008

1 2007

Wyniki wyszukiwania

Calcium transport by mammary secretory cells: mechanisms underlying transepithelial movement

Estrogen regulation and ion dependence of taurine uptake by MCF-7 human breast cancer cells