Author
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Ellis, Kenneth |
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Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Proceedings Publication Acceptance Date: 4/17/1995 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: The potassium (K) content of the fat-free mass (FFM) and body cell mass (BC are assumed constant in adults: 68.1 mEq/kg FFM (Forbes, 1956) and 120 mEq/ BCM (Moore, 1963). The purpose of this study was to derive appropriate K ratios for a pediatric male population. Total body potassium (TBK) was measured by 40K counting. Dual-energy x-ray absorptiometry (DXA) provided measurements of bone mineral content (BMC), fat, and non-fat lean (Lean) tissue masses. BMC was assumed to be a constant fraction of the extracellul solids (ECS). Estimates of total body water were obtained using bioelectrical impedance analysis (TBWBIA), while extracellular water (ECW) were based on Br dilution. The BCM model was BCM = FFMi - ECW - ECS where FFMDXA = Lean + BMC, and FFMBIA = TBWBIA / c, and c was obtained from the Reference Child model (Fomon, 1982). A total of 80 boys (50 White, 22 Blac 8 Hispanic), ages 4-18 yrs, were examined. The K content of FFM and of BCM was found to be significantly less than the classic values for adults. The mean values (+/- SD) were: K/FFMDXA = 58.8 +/- 5.9 mEq/kg; K/FFMBIA = 55.3 +/- 7.2 mEq/kg; K/BCMDXA= 103.9 +/- 14.6 mEq/kg; K/BCMBIA= 92.8 +/- 15.8 mEq/kg. Furthermore, the DXA-derived ratios were not constant over the full age range, whereas the TBW-based ratios were constant only if the hydration factor for the FFM declined with increasing age. |
