Absorption of Calcium in Premature Infants as Measured With a Stable Isotope 46Ca Extrinsic Tag

Ehrenkranz, Richard A.; Ackerman, Barbara A; Nelli, Catherine M; Janghorbani, Morteza

doi:10.1203/00006450-198502000-00006

Cited by 39 publications

(30 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Classical balance studies have suggested an increase in percent net calcium absorption with increasing age but primarily after 4 wk of age (1 I). Ehrenkranz et al (7) found no change in percent calcium absorption with increasing age in a limited number of studies. A large number of infants studied over longer periods of time using this method will be required to address the question of developmental changes in a.…”

Section: Discussionmentioning

confidence: 99%

“…Finally the cost was considerably greater for isotope in these studies. Barltrop et al (1) used 2 mg of 46Ca and Ehrenkranz et al (7) used 20-80 pg/kg of 46Ca orally whereas we have used 7.5 pg/kg 46Ca IV.…”

Section: Discussionmentioning

confidence: 99%

“…Attempts to mimic some of the nutritional factors, such as ca1cium:phosphorus ratios, fat composition, and protein quality, have resulted in premature formulae from which net calcium absorptions have been reported to be 65-75% (15). Using neutron activation of 46Ca given orally, Ehrenkranz et al (7) reported percentages of true calcium absorption of more than 80% in infants fed human milk or premature formula. However, they acknowledge a concern that because isotope was given as a clear solution in the middle of a feeding (and not mixed with the formula) that "some of the enriched calcium may have been absorbed as if from a clear solution rather than as part of a common dietary pool, yielding artificially high values."…”

Section: Discussionmentioning

confidence: 99%

“…Ehrenkranz et al (7) calculated this amount as 0.5% of the administered dose per 24-h period in three infants. Whereas this is small (1.5% in a standard 3-day study), endogenous fecal excretion appears highly variable in preterm infants, and this could represent a significant additional variable in studies (1, 2).…”

Section: Discussionmentioning

confidence: 99%

“…In 1973 and 1977 Barltrop and coworkers (1, 5, 6) used a single oral isotope 46Ca and neutron activation to assess true calcium absorption in premature infants fed several experimental formulas based on standard formula. More recently Ehrenkranz et al (7) used the same single isotope technique, 46Ca by neutron activation, to evaluate premature infants fed either human milk or a premature formula. Although this method allows an assessment of true calcium absorption it remains dependent on complete 72-h stool collection and involves the more cumbersome processing of stool specimens.…”

Section: Discussionmentioning

confidence: 99%

See 4 more Smart Citations

Measurement of True Calcium Absorption in Premature Infants Using Intravenous 46Ca and Oral 44Ca

et al. 1988

View full text Add to dashboard Cite

ABSTRACT. We have developed a method for measuring true fractional calcium absorption (a) in premature infants using two stable isotopes of calcium and tested it in seven studies in seven infants (birth weight 1543 2 65 g, gestation 32.8 f 7 wk). A total of 7.5 pg/kg 46Ca was given as a single intravenous bolus. Immediately thereafter 1.25 mg/ kg of "Ca was given in a single gavage feeding of standard infant formula (Enfamil). A metabolic isolette was used to obtain 4-h collections of urine for 24 h total. 46Ca and 44Ca were measured in urine by thermal ionization mass spectroscopy and expressed as the ratio to naturally occurring 48Ca. The differences in the 46Ca/48Ca and 44Ca/48Ca ratios from natural levels (A% excess 46Ca and A% excess 44Ca) were calculated. Percent absorption (a) equals a constant times cumulative A% excess 44Ca/A% excess 46Ca. The calculation of a is independent of urine volume or concentration. The A% excess 46Ca, showed the expected multiexponential decline as a function of time, and A% excess 44Ca usually peaked during a 4-to 8-h urine collection. Calculations of a using increasingly long sampling times showed that a plateau had been reached by 12 h. a values calculated after 16-24 h in the seven infants at 2 wk of age were 41, 48, 45, 46, 25, 55, and 51%. Repeat studies at 3 wk of age were 46, 60, and 54%. These values are somewhat higher than net percent calcium absorption values reported for standard formula and thus appear very appropriate. This methodology will be very valuable in studying factors that may affect true calcium absorption in premature infants. (Pediatr Res 23: 589-594, 1988) Abbreviations IV, intravenous a, fractional absorption Many factors are known to affect calcium absorption in the adult where calcium absorption is a combination of primarily active and passive transport. Current evidence suggests that in the premature infant these same factors may cause different responses because of differences in both active and passive transport. Characterization of calcium absorption mechanisms in the premature is needed both to understand currently available clinical data and to design feeding regimens that will optimize calcium absorption. In adults, fecal calcium excretion is small and stable. However, in infants endogenous fecal excretion of calcium is very variable and may markedly exceed even urinary excretion of calcium (1-3). Thus traditional balance studies, which measure only net calcium absorption (true absorptionendogenous fecal excretion), are of limited usefulness in characterizing calcium absorption in infants and studying factors affecting calcium absorption. Balance studies that require total collection of stool and urine for periods of usually 72 h also are difficult to carry out in small premature infants who defecate and urinate frequently and whose skin reacts to applied adhesives. Further, cumbersome balance studies limit the ability to conduct repeated studies in the same infant.In adults balance studies often have been supplanted by the use of radio...

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 3 more Smart Citations

Measurement of True Calcium Absorption in Premature Infants Using Intravenous 46Ca and Oral 44Ca

et al. 1988

View full text Add to dashboard Cite

show abstract

Erythrocyte incorporation of ingested stable isotope of iron (⁵⁸Fe)

1986

Self Cite

View full text Add to dashboard Cite

Because of a possible hazard from the use of radioisotopes to determine iron absorption by infants, the use of stable isotopes for this purpose has much appeal. We have applied the method of inductively coupled plasma mass spectrometry (ICP/MS) to determine the mass ratio, 58Fe/57Fe, in blood before and after oral administration of 58Fe. From the increase in erythrocyte enrichment with 58Fe, we have calculated percentage absorption of iron. We have shown that the coefficient of variation of measured mass isotope ratio is 0.1-1.0%, depending on the conditions of the measurement. The method has been applied to a feasibility study involving four infants. Each infant was given 58Fe either as a single dose or as one dose on each of two consecutive days. Each dose provided 1.945 mg iron and 1.440 mg 58Fe. Samples of blood were obtained before isotope administration and at 14, 42, and 60 days thereafter. Isotopic analysis of the samples demonstrates that this approach results in a sufficiently large isotope enrichment to permit satisfactory measurement of iron availability. It is concluded that this new method is highly promising for studies of iron availability in infants and children.

show abstract

Plasma kinetics of magnesium and calcium stable isotope tracers in a human subject after simultaneous oral ingestion of25Mg and44Ca determined by thermal ionization mass spectrometry

Stegmann¹,

Karbach²

1993

Biol. Mass Spectrom.

View full text Add to dashboard Cite

The plasma concentrations of stable isotope tracers of magnesium (25Mg) and calcium (44Ca) were determined during a 50 h period, after simultaneous oral tracer ingestion in an adult man. The measurements were performed by magnetic sector field mass spectrometry using surface ionization ion sources. The data were used to evaluate the potential of this method in long-term kinetic studies. It is concluded that under the experimental conditions specified, the isotopic tracers will be detectable in blood plasma with sufficient precision and accuracy for approximately 600 h after oral ingestion. The differences in the plasma concentration curves of 25Mg and 44Ca were analysed by means of the convolution integral method. These differences indicate inhomogeneities in the distribution of absorption activity relative to magnesium and calcium within the upper small intestine.

show abstract

Absorption of Calcium in Premature Infants as Measured With a Stable Isotope 46Ca Extrinsic Tag

Cited by 39 publications

References 17 publications

Measurement of True Calcium Absorption in Premature Infants Using Intravenous 46Ca and Oral 44Ca

Measurement of True Calcium Absorption in Premature Infants Using Intravenous 46Ca and Oral 44Ca

Erythrocyte incorporation of ingested stable isotope of iron (⁵⁸Fe)

Plasma kinetics of magnesium and calcium stable isotope tracers in a human subject after simultaneous oral ingestion of25Mg and44Ca determined by thermal ionization mass spectrometry

Contact Info

Product

Resources

About

Absorption of Calcium in Premature Infants as Measured With a Stable Isotope 46Ca Extrinsic Tag

Cited by 39 publications

References 17 publications

Measurement of True Calcium Absorption in Premature Infants Using Intravenous 46Ca and Oral 44Ca

Measurement of True Calcium Absorption in Premature Infants Using Intravenous 46Ca and Oral 44Ca

Erythrocyte incorporation of ingested stable isotope of iron (58Fe)

Plasma kinetics of magnesium and calcium stable isotope tracers in a human subject after simultaneous oral ingestion of25Mg and44Ca determined by thermal ionization mass spectrometry

Contact Info

Product

Resources

About

Erythrocyte incorporation of ingested stable isotope of iron (⁵⁸Fe)