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RELIABLE ASSAYS FOR DETERMINING ENDOGENOUS COMPONENTS OF HUMAN MILK
Citation:
HINES, E. P., J. RAYNER, R. R. BARBEE, B. HEIDENFELDER, R. A. MORELAND, A. VALCOUR, J. E. GALLAGHER, AND S. E. FENTON. RELIABLE ASSAYS FOR DETERMINING ENDOGENOUS COMPONENTS OF HUMAN MILK. Presented at Society of Toxicology, San Diego, CA, March 05 - 09, 2006.
Description:
Healthy women from 18-38 years old (N=25) fasted for several hours and twice donated blood and milk (postpartum 2-7 weeks and 3-4 months) for the EPA's Methods Advancement for Milk Analysis study, a pilot for the National Children's Study (NCS). Endogenous components were chosen for comparison in these fluids based on their potential as NCS biomarkers for children's health. Our goal was to determine if validated high throughput methods for selected serum analytes could be applied for use in breast milk (high throughput assays are limited), and if serum is a satisfactory surrogate for determining levels in milk. Since the NCS is planning to collect samples during lactation, we also attempted to define 'normal' ranges for these components in milk (traditionally defined in non-lactating women). Reliable methods were developed for 7 of 8 chosen components of milk, based on assay sensitivity, linearity of response, and precision (dilution and spike recovery). Assays to measure leptin in milk were not reliable. However, assays were successful for estradiol, prolactin, tumor necrosis factor-alpha (TNFa), interleukin 6 (IL6), triglycerides, glucose, and IgA (secretory form in milk). None of the components demonstrated an identical range in values in blood and milk, and glucose was the component whose blood/milk range of values was most similar (about 3-fold range in milk, 2-fold in serum). The data showed similar intra-individual serum IgA and TnFa levels between collections. Donors with high milk sIgA also had elevated milk IL6. In addition, a subset of donors' samples was analyzed fresh (maintained at 4C) and frozen on the same day to determine the contribution in assay variability from freeze-thawing. Prolactin levels were consistently lower in fresh vs. frozen milk samples. (This abstract does not necessarily reflect EPA policy.)