Making Isotonic Milk: Focus on " Ca 2+ -activated Cl − Channel Currents in Mammary Secretory Cells from Lactating Mouse. " 2 3

1 lactating mouse.” 2 3 Bruce D Schultz* 4 5 Department of Anatomy & Physiology, Kansas State University College of Veterinary Medicine, 6 Manhattan, KS, USA 7 8 * Corresponding Author: 9 10 Bruce D. Schultz, Ph.D. 11 Professor and Interim Head 12 Department of Anatomy and Physiology 13 1620 Denison Avenue, 127 Coles Hall 14 Manhattan, KS 66506 15 USA 16 [email protected] 17 18 19 The very essence of mammals as a taxonomic class is based on the mammary gland and the ability to 20 provide milk as a total and sole nutritional source at the start of post-partum life. However, much 21 remains to be learned regarding epithelial cellular mechanisms that account for milk composition and 22 volume. In part, this lack of knowledge may reflect the complex interplay of hormones that contribute to 23 gland development during puberty and gestation, to the regulation of activity during lactation, and to 24 the systematic involution of the gland at weaning. Further complicating the scheme is the wide diversity 25 in milk compositions and suckling patterns across the class (6). There is, however, great impetus to fully 26 describe mammary cell function. First, breast feeding is widely practiced in developing countries and 27 there is a re-awakening to health benefits associated with breast-feeding in developed countries as it 28 may impact health status throughout life. Second, the dairy industry comprises the largest economic 29 segment of animal agriculture in North America and mastitis is the most costly single medical condition 30 in production agriculture. Third, breast cancer ranks first for incidence and second for cause of death in 31 women, with roughly 80% of breast cancers being of epithelial cell origin. Thus, strong arguments can be 32 made on academic, clinical and economic grounds to develop a greater understanding of mammary 33 epithelial function at the cellular level. 34