Effects of sex steroids on normal human breast : studies in vivo using microdialysis and in vitro in cell culture

• Prolonged exposure to sex steroids may constitute a risk factor for the development of breast cancer. The biological mechanisms involved in breast carcinogenesis are not well understood.Basic knowledge of sex steroid effects on the normal human breast is still limited, one reason being the lack of an available in vivo technique for investigations of breast tissue metabolism.In this study, the microdialysis technique was developed and evaluated as a method for measurements of tissue-specific concentrations of amino acids, lactate, pyruvate and glutathione in normal human breast tissue during the menstrual cycle. The technique was successfully applied to breast tissue and it was observed that the concentrations of several amino acids as well as glutathione changed during the menstrual cycle. Oxidative damage to cells is one of the mechanisms which may be involved in the development of breast cancer. Normal aerobic metabolism generates potentially dangerous oxidants which are controlled by a variety of antioxidant systems. The exact regulatory mechanisms of these systems are not yet fully understood. We studied the effects of estradiol and progesterone on antioxidative activity in normal human breast tissue, in vivo with the microdialysis technique, and in vitro using normal human breast epithelial cells in culture. The in vivo levels of the antioxidant glutathione were measured early and late in the menstrual cycle in breast tissue and subcutaneous fat. The glutathione levels were higher late in the menstrual cycle in both tissues, when the serum levels of estradiol and progesterone were high. In vitro, breast epithelium exposed to estradiol and progesterone exhibited decreased activity of the antioxidative enzymes catalase and glutathione reductase, whereas the activity of glutathione peroxidase tended to increase compared with cells grown in medium without added sex hormones. The vulnerability to oxidative stress, induced by hydrogen peroxide, increased in cells grown with estradiol and progesterone present in the media. α-Tocopherol, and α-tocopherol in combination with ascorbic acid, but not ascorbic acid alone, protected from cell death induced by hydrogen peroxide. This effect was not dependent on estradiol and progesterone exposure.In conclusion, the data suggest an effect of estradiol and progesterone on antioxidative activity in normal human breast tissue both in vivo and in vitro.Microdialysis will be a useful tool in future research of these and other aspects concerning human breast tissue.

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