x-ray fluorescence microscopy reveals accumulation and secretion of discrete intracellular zinc pools in the lactating mouse mammary glandx射线荧光显微镜揭示积累和分泌的离散哺乳期小鼠乳腺细胞内锌池.pdfVIP

X-Ray Fluorescence Microscopy Reveals Accumulation and Secretion of Discrete Intracellular Zinc Pools in the Lactating Mouse Mammary Gland 1 1 2 2 1 Nicholas McCormick , Vanessa Velasquez , Lydia Finney , Stefan Vogt , Shannon L. Kelleher * 1 Department of Nutritional Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America, 2 Argonne National Laboratory, Argonne, Illinois, United States of America Abstract Background: The mammary gland is responsible for the transfer of a tremendous amount of zinc ( ,1–3 mg zinc/day) from maternal circulation into milk during lactation to support the growth and development of the offspring. When this process is compromised, severe zinc deficiency compromises neuronal development and immune function and increases infant morbidity and/or mortality. It remains unclear as to how the lactating mammary gland dynamically integrates zinc import from maternal circulation with the enormous amount of zinc that is secreted into milk. Methodology/Principal Findings: Herein we utilized X-ray fluorescence microscopy (XFM) which allowed for the visualization and quantification of the process of zinc transfer through the mammary gland of the lactating mouse. Our data illustrate that a large amount of zinc first accumulates in the mammary gland during lactation. Interestingly, this zinc is not cytosolic, but accumulated in large, discrete sub-cellular compartments. These zinc pools were then redistributed to small intracellular vesicles destined for secretion in a prolactin-responsive manner. Confocal microscopy identified mitochondria and the Golgi apparatus as the sub-cellular compartments which accumulate zinc; however,