Studies on Erythro‐Kinetics in Infancy:The Long‐Term Behaviour of Radioiron in Circulating Foetal and Adult Haemoglobin, and its Faecal Excretion1

Abstract

Previous studies on the relative rate of synthesis of haemoglobin F and A in infants by Garby, Sjolin & Vuille [7] have shown that intravenously injected radioiron is incorporated into both haenioglobin A and haemoglobin F during the first months of life. Five of the infants studied were followed up for periods ranging from 58 to 123 days after injection of the isotope. The age a t injection was between 5 and 25 days. I n all five cases the total amount of radioactivity present in the circulating total haemoglobin (haemoglobin A and F) was recorded a t time intervals of about one week. I n three of the infants the excretion of radioiron in the faeces was also measured. The present paper comprises a description of the behaviour of radioactive iron in such longterm studies. The results have bearing on several aspects of ferro-erythro-kinetics in infancy, and extend and corroborate earlier findings by us [S] concerning the short-term behaviour of radioiron in this This investigation was supported by grants from the Swedish Medical Research Council and by grants (Research Project 154/RB) from the International Atomic Energy Agency, Vienna.3 -642879 Aeta Prediatrica Val. 53 age group. Furt'hermore, a new approach is presented for calculating the daily excretion of iron in young infants. MaterialThe clinical data concernipg the five patients Li, B1, Sj, Lo, and Ja have been presented in a previous paper [7]. All were considered t o be haematologically normal (infant Lo had a rather low haemoglobin concentration during the latter part of the study, and will be disciissetl in greater detail). Two of the infant>s, B1 and Ja, suffered from myelomeningocele and hydrocephalus, but t'hey had no further complications during the period of investigation. All infants were fed with breast milk during the first 2 to 4 weeks of life; t.hey were subsequently given different cow-milk mixtures providing a daily intake of iron of 1-2 mg/kg body weight. MethodsThe methods used t o measure the amount of radioactivity present in total haemoglobin, haemoglobin A and F have been reported [6. 7, 81. In calculating the blood volume, a correction factor was introduced in order t o compensate for the frequent blood sampling. This factor amounted to 5-10% of the total blood volume at the end

Erythrocyte incorporation of iron by infants: iron bioavailability from a low-iron infant formula and an evaluation of the usefulness of correcting erythrocyte incorporation values, using a reference dose or plasma ferritin concentrations

“…This methodology assumes that a large proportion of newly-absorbed Fe is readily incorporated into erythrocytes. Although some information is available on erythrocyte incorporation of injected Fe in very young infants (Garby et al 1964) and in low-birth-weight infants (Gorten et al 1963;Ehrenkranz et al 1992;Zlotkin et al 1995), no studies have been reported on erythrocyte incorporation rate of absorbed Fe in older, term infants. Recently, significant differences between Fe retention (based on 11 d faecal collections) and erythrocyte incorporation of 58 Fe were reported in term infants (Fomon et al 2000).…”

Scientific Opinion on Dietary Reference Values for iron

“…faecal, urinary and dermal) losses, the increase in haemoglobin mass, the increase in tissue iron and the increase in storage iron. Considering median body weights at 6 and 12 months (Dibley et al, 1987) and reference body weights from NHANES III (1988)(1989)(1990)(1991)(1992)(1993)(1994), a CV for weight of 10 % and an estimated basal iron loss of 0.03 mg/kg body weight per day (Garby et al, 1964), and assuming its variability is proportional to the variability of weight, the mid-range estimate of basal losses for infants aged 6-12 months was calculated to be 0.26 ± 0.03 mg/day. The median weight increment was assessed to be 0.39 kg/month or 13 g/day (Dibley et al, 1987), considering a CV of 50 %.…”

Reticulocyte hemoglobin content changes after treatment of anemia of prematurity

“…The RET‐He trends obtained in the present study suggest that ID in the central nervous system may be present for a longer period in VLBW infants. Previous report suggested that preterm infants absorb ingested iron at a high rate, although a very small proportion of the absorbed iron is used promptly for Hb synthesis 31,32 . The relatively large amount of iron that is not used immediately likely enters storage sites.…”