No abstract
Oral iron and the bioavailability of zinc N J MEADOWS, S L GRAINGER, WARWICK RUSE, P W N KEELING, R P H THOMPSON Abstract The oral bioavailability of zinc was studied in nonpregnant adults before and 24 hours after two weeks of oral supplementation with iron and folic acid. Bioavailability was greatly reduced, and the shape of the plasma curves suggested that this was due to impairment of the intestinal absorption of zinc. The findings suggest that the reduced bioavailability of zinc occurs because of interelement competition in the bowel wall. This might induce zinc depletion.
1. 65Zn was injected intravenously during transjugular liver biopsy and, from simultaneous hepatic and peripheral venous blood samples, hepatointestinal 65Zn extraction was calculated. Hepatic zinc content was measured in biopsy specimens. 2. On the same occasion samples of liver tissue were taken and their zinc content was measured by atomic absorption spectrophotometry. 3. Seven patients with cirrhosis had significantly lower hepatic zinc content and hepatointestinal zinc extraction than six control patients with mild liver disease. Six patients with chronic hepatitis had a mean hepatointestinal zinc extraction higher than control patients, whereas their mean hepatic zinc content was lower, although the former difference did not achieve statistical significance. 4. These results demonstrate that hepatointestinal extraction of zinc is impaired in cirrhosis, but not in chronic hepatitis.
SUMMARY The zinc content of peripheral blood leucocytes from the cord blood of 63 normal and 20 preterm babies, and of 27 babies with evidence of idiopathic intrauterine growth retardation (IUGR) was measured. Leucocyte zinc depletion was present in babies with acute IUGR (IUGR babies compared with controls, mean 47-8 v 515 ng zinc/mg dry weight), but was especially severe in those with prolonged IUGR (mean 43 -2 ng zinc/mg dry weight), while preterm babies were normal (mean 51 * 9 ng zinc/mg dry weight). We suggest that this fetal tissue zinc depletion is caused by maternal zinc depletion, and may reflect a reduction of whole body zinc status.To estimate the whole body content of an element that is predominantly intracellular, it is necessary either to measure its intracellular content or some extracellular index that reflects accurately intracellular changes. We have shown that peripheral blood leucocytes represent a suitable nucleated tissue in which to measure zinc and predict the cxtrahepatic nucleated tissue status.'We reported that low values of zinc in maternal peripheral blood leucocytes are strongly associated with idiopathic intrauterine growth retardation (IUGR).2 Small for gestational age infants have both an increased morbidity-minor neurological problems, learning disorders, and susceptibility to infections-and early mortality.3 Neonatal zinc deprivation is associated with thymic atrophy and defective cellular immunity and, in the more extreme forms, with skin rashes and diarrhoea. During the first 6 months after birth, small babies show increased growth velocity (or so called catch-up growth) and requirements for zinc, suggesting that intrauterine growth may have been limited by the supply of zinc.4 The bio-availability of zinc in breast milk is greater than that in formula feeds,5 but if maternal zinc depletion has already caused neonatal deprivation of this element, then it is unlikely that the mother's milk content will be adequate to correct the imbalance.We have compared the results of maternal and fetal plasma and peripheral blood leucocyte zinc of normal, premature, and growth retarded babies and corresponding mothers to determine whether there is a relation between the values of maternal and fetal zinc and IUGR. Patients and methodsWe studied 110 mothers and babies: 63 mothers giving birth to normal babies; 20 to premature babies (gestational age assessed by Dubowitz score <37 weeks, and appropriate weight for age); 19 to acute onset idiopathic IUGR babies (gestational age >37 weeks and weight only below 10th centile); and 8 to chronic idiopathic IUGR babies (weight, length, and head circumference all below the 10th centile). All were assessed by the neonatal team.Simultaneous samples (30 ml) of venous maternal and clamped, pulseless, umbilical cord blood were taken into heparinized syringes and the leucocytes separated.6 The isolated leucocytes were dried to constant weight, the zinc was extracted with 1.0 M hydrochloric acid and measured by atomic absorption flame spectrophotometry (AAS...
1. In nine patients with chronic liver disease photoreceptor function was tested, by measurement of the B-wave amplitude of dark adaptation by electroretinography, and the leucocyte content and plasma concentration of zinc were determined. 2. Four of the patients were leucocyte zinc-depleted and had impaired photoreceptor function, but this was normal in the five with normal leucocyte zinc content.
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