Preliminary exploration into the physiology of the resting breast

Background Epidemiological and animal data are clear that early first pregnancy decreases subsequent breast cancer risk. The mechanism for this decrease however is less clear and several hypotheses abound. One possibility that has not received any attention is the physiology of fluid secretion in the breast. The ductal systems have secretions which can be accessed either through nipple aspiration or ductal lavage. It is not clear whether the mechanisms identified for absorption, secretion, concentration and local synthesis that have been described in the lactating breast are consistently available to the non lactating breast or whether there is a difference in nulliparous and parous women. It is not clear whether the known changes to the ductal-alveolar system with the first pregnancy remain permanent or have long lasting ramifications. The hypothesis tested was that the first pregnancy permanently changes the physiology of the ductal epithelial membrane transport. Two known drug transport mechanisms in lactating women were tested using caffeine and cimetidine.