Dynamics of Calcium Metabolism in Infancy and Childhood. I. Methodology and Quantification in the Infant

Moore, L. J.; Machlan, L. A.; Lim, Mary O.; Yergey, Alfred L.; Hansen, James

doi:10.1203/00006450-198519040-00001

Cited by 45 publications

(30 citation statements)

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“…However, that study used a single orally administered Ca isotope, and Vf was calculated indirectly based on mass balance and fecal isotope recovery data. Using a similar technique, Senterre (25) found much lower rates (17 mg/kg/d) for Vf in LBW infants, as did Moore et al (20) in a small study ( n = 2) using an i. (15) demonstrated that Ca absorption in adults measured by dual tracer stable isotope studies is comparable to that obtained from mass balance.…”

Section: Discussionmentioning

confidence: 56%

“…This pool is believed to consist of plasma and some components of extracellular fluid and surface bone. Ca flow to stable bone from the central pool may involve intermediate, kinetically determined bone pools; however, these do not affect the calculation of Vr or V, (19)(20)(21). With this assumption, the ratio Vf/V, is equal to the ratio of the accumulated tracer A period of time (t) is chosen such that the recovery of the tracer has neared "completeness," that is, the curve of accumulated tracer recovery has achieved an asymptotic value.…”

Section: : 615-6181991)mentioning

confidence: 99%

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Dual Tracer Stable Isotopic Assessment of Calcium Absorption and Endogenous Fecal Excretion in Low Birth Weight Infants

et al. 1991

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ABSTRACT. Using a dual tracer (44Ca orally and 46Ca studies of Ca balance in infants because the mass balance techi.v.) stable isotope technique, true dietary Ca absorption, nique does not differentiate between unabsorbed and endogeendogenous fecal Ca excretion, and net Ca retention were nously excreted fecal Ca. measured in 12 low birth weight (1426 + 260 g) infants The use of stable isotopes of Ca allows for the direct measurefed a high Ca-containing formula. Endogenous fecal Ca ment of Vj without requiring exposure to ionizing radiation. V, excretion averaged 7.2 2 4.1 % of intake, and exceeded and Vs can be determined from the simultaneous administration 10% of intake in three infants. Net Ca retention, 103 2 38 of both i.v. and oral isotopic tracers with subsequent monitoring mg/kg/d, was consistent with previous studies of Ca reten-of fecal and urinary tracer excretion (1 1-17). In this study, we tion obtained using mass balance techniques and correlated used 44Ca and 4('Ca to measure V, and VS in a group of healthy, closely (r = 0.98, p < 0.001) with true Ca absorption but growing, LBW infants. The objectives of our study were to not with endogenous fecal excretion (r = -0 . 4 0 ,~ = 0.19). measure the rates of V, and Vf in LBW infants on a fixed, high Although endogenous fecal excretion may represent a sig-Ca-containing diet and to determine their relationship to V,. nificant source of Ca loss for some low birth weight infants, these data suggest that net Ca retention in low birth weight MATERIALS AND METHODS infants fed a high Ca-containing formula is primarily determined by the total dietary Ca absorbed. (Pediatr ResPatient population. Infants admitted to the neonatal intensive 29: 615-618,1991)care units at Holy Cross Hospital, Silver Spring, MD, and Children's National Medical Center, Washington, DC, who weighed Abbreviations between 750-1750 g at birth, and whose mothers chose not to breast feed, were eligible for enrollment in this study. A dual LBW, low birth weight tracer stable isotope study, with subsequent 24-h urine and 96-h V,, endogenous fecal Ca excretion stool collections, was conducted when the infants were receiving Vi, Ca intake complete enteral nutrition of the designated formula for a min-V,, true dietary Ca absorption imum of 1 wk and were free of medical illnesses. At the time of V., urinary Ca excretion the study, all patients were free of ventilatory support, diuretics, V,, net Ca retention (bone accretion) and antibiotic therapy. Three infants (CB, BH, and RM) were receiving caffeine. No patient had received steroids postnatally. The study was approved by the Institutional Review Committee of the National Institute of Child Health and Human Development and by the review committees of the respective hospitals. Numerous recent studies in LBW infants have assessed the Informed written consent was obtained from the parents prior bioavailability of Ca in special formulas containing high concen-to enrollment in the study. trations of Ca relative to human milk. However, these studies I...

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Section: Discussionmentioning

confidence: 56%

Section: : 615-6181991)mentioning

confidence: 99%

Dual Tracer Stable Isotopic Assessment of Calcium Absorption and Endogenous Fecal Excretion in Low Birth Weight Infants

et al. 1991

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“…This method has been used extensively with radio tracers to determine absorption of calcium in adults (1 8). It has also been used with stable isotopic tracers to determine calcium absorption by infants (1,5,19). The procedure is expressed analytically by equation 1:…”

Section: Methodsmentioning

confidence: 99%

Absorption of Calcium and Magnesium from Fortified Human Milk by Very Low Birth Weight Infants

et al. 1989

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ABSTRACT. Absorption of calcium and magnesium endogenous to human milk, as well as calcium and magnesium added as an exogenous supplement to human milk, was determined in 9 very low birth wt infants. Human milk, intrinsically labeled with stable isotopic tracers of calcium and magnesium, was prepared by administering isotopic tracers intravenously to a lactating woman. Different isotopic tracers, which were representative of calcium and magnesium in the supplement (Enfamil Human Milk Fortifier, Mead Johnson Nutritional Div.), were added to the intrinsically labeled milk. The fortified milk, which was labeled with two calcium tracers and two magnesium tracers, was given orally to the test subjects in a single feeding. True absorption of calcium and magnesium was determined from differences between the doses of tracer ingested and the quantities of tracer excreted in the feces. Stable isotopic tracers were quantified by fast atom bombardment mass spectrometry. These results demonstrate that the fractional absorptions of calcium in the human milk and the added mineral supplement are 80 and 82%, respectively. A total of 89% magnesium endogenous to human milk and 86% of magnesium derived from the mineral supplement was absorbed by the VLBW infants. The need to better define the optimum calcium intake of VLBW infants has been discussed by Ehrenkranz et al. ( I ) who used a stable isotopic tracer to determine calcium absorption in premature infants. As it has been previously established with radioisotopic tracers that calcium absorption by adults is 25 to 35% (2), it is surprising to find that 84% of the dietary calcium was absorbed by preterm infants. Although VLBW infants do have an unusually high need for calcium (3, 4), it was also recognized that this unexpectedly high value reflects calcium

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“…Stable calcium isotope tracers have been used extensively for ϳ30 years for metabolic studies of calcium homeostasis in humans in a variety of clinical areas (1)(2)(3)(4)(5)(6)(7). Stable isotopes are safe for use in humans of all ages and do not have problems related to the disposal of contaminated waste, a major advantage over radioisotopes.…”

confidence: 99%

“…This is because virtually all of these studies have used analytical approaches in which 500 L or more of serum was required for the oxalate precipitation or ion-exchange methods used to prepare the samples for analysis. Most analyses have involved thermal ionization mass spectrometry (TIMS), 3 using either quadrupole or magnetic sectorbased spectrometers (1,2 ).…”

confidence: 99%

Inductively Coupled Plasma Mass Spectrometric Analysis of Calcium Isotopes in Human Serum: A Low-Sample-Volume Acid-Equilibration Method

et al. 2003

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Background: Analytical methods for measuring the calcium isotope distribution in enriched human serum samples that use low blood volumes, simple preparation methods, and rapid analysis are important in clinical studies of calcium kinetics. Previously, sample preparation by oxalate precipitation typically required 500 L of serum. This method was time-consuming, and the blood volume required was limiting in circumstances when only a small amount of serum could be obtained. Methods: Serum was collected from humans who were administered 42 Ca, and 20 L of serum was mixed with 2 mL of 0.22-0.67 mol/L HNO 3 at room temperature for between 1 min and 16 h. The 42 Ca/ 43 Ca ratio in the supernatant was measured by a magnetic sector inductively coupled plasma mass spectrometer (ICP-MS). Calcium isotope ratios from these equilibration solutions were compared with data from oxalate-precipitated serum samples to determine the optimum equilibrium time and the effect of acid concentration on equilibrium. Results: Various amounts of aggregated particles developed in different acid-serum mixtures. These affected the time required for isotope equilibration in the mixture. The shortest equilibrium time needed for the calcium isotopes varied from 1 to 6 h for samples acidified with 0.22-0.45 mol/L HNO 3 . Data obtained from these solutions were consistent with data from oxalate-precipitated calcium. The precision of 42 Ca/ 43 Ca ratio measurements was better than 0.5%.

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Dynamics of Calcium Metabolism in Infancy and Childhood. I. Methodology and Quantification in the Infant

Cited by 45 publications

References 0 publications

Dual Tracer Stable Isotopic Assessment of Calcium Absorption and Endogenous Fecal Excretion in Low Birth Weight Infants

Dual Tracer Stable Isotopic Assessment of Calcium Absorption and Endogenous Fecal Excretion in Low Birth Weight Infants

Absorption of Calcium and Magnesium from Fortified Human Milk by Very Low Birth Weight Infants

Inductively Coupled Plasma Mass Spectrometric Analysis of Calcium Isotopes in Human Serum: A Low-Sample-Volume Acid-Equilibration Method

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