Epsilon Archive for Student Projects

Abstract

Milk is the most important nutrition source for breast-fed infants and an important food item for high-milk consumers. However, a wide variety of chemicals can be transported into milk, which can be of great concern from a food safety perspective. The active transport protein, breast cancer resistance protein (BCRP), is highly upregulated in lactating mammary gland in mouse, cow and human. BCRP belongs to the superfamily of ABC transporters and export a wide variety of chemicals from the cells. Udder inflammation (mastitis) is a common bacterial infection among dairy cows. In subclinical mastitis, the cow has no visible illness and delivers milk, but the milk is of poor quality and the milk yield is reduced.

In this project, an in vitro cell model has been optimised and used for studies of active transport of chemicals in normal murine mammary epithelial HC11 cells. Determination of transport has been performed by radioactivity measurements and liquid chromatography-masspectrometry. Tritium labelled mitoxantrone was used as a model substance for BCRP transport. The effects on gene expression of BCRP and the milk protein β-casein of differentiation of cells and after Staphylococcus aureus infections have been examined by real time RT-PCR as well as mitoxantrone transport in infected cells.

Only a minor part of the total mitoxantrone transport in the HC11 cell line was mediated by BCRP. Neither albendazole sulfoxide, an anti-parasitic drug widely used in human and veterinary medicine, nor genistein, a phytoestrogen from soya beans and red clover, are substrates and/or inhibitors of BCRP in this cell line under the experimental conditions used. The S. aureus infection decreased synthesis of β-casein, but did not affect BCRP, thereby, the HC11 cell line has a potential to be used as an in vitro model of mastitis. In addition, mitoxantrone transport was unaffected by infection.

Since the HC11 cell line derives from a normal mammary gland, it is expected to express BCRP levels likely to be found in in vivo, and thereby an interesting model for in vitro studies of chemicals secretion into milk. However, the cell line has to be characterized more and the methods standardised before usage.