The presence of lactose in nipple secretions is considered biochemical evidence of breast secretory activity, and has been reported to occur more frequently in white compared to brownish or green colored breast fluid. We studied lactose, Na+, and K+ concentrations, the Na+/K+ ratio, and the coloration of nipple aspirate fluid (NAF) from 49 nonpregnant women. A significant relationship was found between the concentrations of lactose, Na+, and K+, and age and the coloration of NAF. Lactose was present in 22/49 (44.8%) of the NAF samples and declined with age from 100% positivity in women less than or equal to 29 years to 29% in those less than or equal to 35 years. In NAF of deep yellow, brown and green colorations, only traces of lactose were found. Na+ and K+ increased with age and with darker colorations compared to white, pale yellow, or colorless NAF. Lactose was present in NAF samples from both parous and nulliparous younger women, indicating that the breasts of many nonpregnant women respond to prolactin stimulation; hence, lactose may provide a simple marker indicating active physiologic secretory activity of the breast. As reported previously, NAF of darker coloration, containing elevated levels of cholesterol, cholesterol oxidation products, and other substances, suggests retention and impaired reabsorption of these and other products of secretion. Because of the secretion and temporary retention by the breast glands of chemical substances of exogenous and endogenous origin, including mutagens and carcinogens, lactose concentration and coloration of NAF may be useful as markers of secretion and reabsorption in future physiologically based clinical and epidemiologic studies of the pathogenesis of breast disease.

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The coloration of nipple aspirates of breast fluid from 2,343 women were compared with breast fluid concentrations of cholesterol. cholesterol epoxides, lipid peroxides, estrogens, and immunoglobulins. Darker-colored breast fluid had significantly higher mean concentrations of cholesterol, cholesterol epoxides, lipid peroxides, and estrogens than did lighter-colored fluids, whereas no relationship of coloration with immunoglobulin levels was found.

Sprague-Dawley rat mammary gland is extremely sensitive to tumorigenesis by single or multiple doses of several polycyclic aromatic hydrocarbons. We obtained quantitative data on the in vitro mutagenic activation of several procarcinogens by 9000 g supernatant fraction (S9) from rat mammary gland using the Ames test. Mutagenic activation was shown to be dependent on a nicotinamide adenine dinucleotide phosphate (NADPH) generating system. An S9 preparation from mammary tissue of lactating Sprague-Dawley rats was shown to activate 2-aminoanthracene (2-AA). A polychlorinated biphenyl mixture of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) given to rats greatly raised the specific activity (revertant TA98 colonies/mg S9 protein) of the mammary tissue using 2-AA as a test carcinogen, and permitted detection of 2,4-diaminoanisole (DAA) and 2,7-diaminofluorene (DAF) activation. Procarcinogens 2-aminofluorine (2-AF), benzo[a]pyrene (BP) and aflatoxin (AFL) B1 were not detectably activated by mammary gland. Mutagenesis produced in mammary S9 activation of 2-AA, DAA or DAF was significantly inhibited by alpha-naphthoflavone (alpha NF) but was inhibited minimally by metyrapone (MP). Human mammary tumor cell lines (734B, SkBr3, MDA-MD-330) possessed inducible procarcinogen metabolizing activities similar to those found in S9 of rat mammary tissue. We demonstrated a simple and convenient use of the Ames test to characterize activation of many potential mutagens and carcinogens for mammary gland. When a test compound such as 2-AA was used, selective enzyme induction and inhibition was demonstrated.

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