Urinary iodine excretion in pregnant women as an index of the impact of a national iodization programme

OBJECTIVE

To evaluate the extent to which increase in iodine requirement was achieved in pregnant women who attended the antenatal clinic at Harare Central Hospital.

DESIGN

Cross sectional.

SETTING

Samples were collected from pregnant women attending antenatal clinic at Harare Central Hospital, and from lactating mothers and their infants.

SUBJECTS

100 pregnant women attending the antenatal clinic at Harare Central hospital, 80 infants, 80 lactating women and 18 non-pregnant women.

MAIN OUTCOME MEASURES

Comparison of urinary iodine excretion levels among pregnant women, lactating mothers and their infants.

RESULT

The results indicated lower urinary iodine excretion levels for the pregnant women and lactating mothers compared to the urinary iodine excretion of the infants and the breast milk iodine content. The urinary iodine excretion level of the non-pregnant control women was median (first and third quartiles): 18.5 microg/dl (30.0, 30.2 microg/dl). The urinary iodine excretion level of the lactating mothers was median (first and third quartiles): 12.0 mg/dl (7.6, 19.5 mg/dl) compared to the level of the infants, median (first and third quartiles): 26.5 mg/dl (18.8, 11.5 mg/dl). A significant difference was noted between the median urinary iodine excretion levels of the mothers, and the median levels of the infants, p = 0.001. The mean milk iodine content was 21.2 +/- 6.8 mg/dl. There was no correlation between breast milk iodine levels and the urinary iodine excretion levels of the infants, (p = 0.96, r = 0.006). Positive correlation was found between maternal urinary iodine excretion levels and the urinary iodine excretion levels of the infants, p = 0.016 r = 0.285. Serum FT4, and TSH levels were found to be higher for infants at six weeks after birth, (FT4 =20.91 +/- 5.65 pmol/L) and median TSH = 2.28 mIU/ml (1.36, 0.86) mIU/rnl, compared to levels at 12 weeks postpartum: (FT4 = 17.53-*6.4 pmol/L) and median TSH = 2.02 mIU/ml, (0.84, 1.55) mIU/ml. The differences were not significant.

CONCLUSION

The results indicated a significant reduction in the urinary iodine content of pregnant women, and lactating mothers which did not appear to have any relationship to the urinary iodine excretion levels of infants and iodine content of breast milk. Iodine intake needed to be raised to reflect the recent proposed recommendations.

Vitamin A status of term and preterm infants delivered at Harare Central Hospital and fed exclusively on breast milk

OBJECTIVE

To investigate the vitamin A status of pregnant mothers, lactating mothers, preterm and term infants who were being fed exclusively on breast milk.

DESIGN

Systematic/cross sectional.

SETTING

Vitamin A research laboratory, animal science research laboratory, University of Zimbabwe, and Harare Central Hospital.

SUBJECTS

105 pregnant mothers attending the antenatal clinic at Harare Central Hospital for a routine check up were recruited for the study. Two groups of infants: those born at term and those with gestational age < or = 36 weeks.

MAIN OUTCOME MEASURES

Serum retinol levels of infants/mothers pairs. Breast milk retinol levels.

RESULT

The serum retinol levels for the infants were similar irrespective of age with a mean of 26.15 +/- 9.78 microg/dl. There was no statistically significant difference. The mean serum retinol levels of infants and mothers were significantly different, (p = 0.001). With mother/infant ratio of serum retinol concentration of 1.7:1. Maternal serum retinol levels correlated positively with infant serum retinol levels, r = 0.728. Forty four percent of the preterm and 17% of the term infants had serum retinol levels < 20 microg/dl, indicating deficiency, 2 and only 20% of the infants had retinol levels > 40 microg/dl.

CONCLUSION

The majority of infants might be at risk of vitamin A deficiency. Increased intake of vitamin A in pregnant women is necessary, and direct vitamin A supplementation of infants should be considered.

Evidence of grave vitamin A deficiency among lactating women in the semi-arid rural area of Makhaza in Zimbabwe. A population-based study

OBJECTIVE

To assess the vitamin A and iron status of lactating women.

DESIGN

A population-based cross-sectional descriptive study.

SETTING

A semi-arid rural area of Makhaza in Zimbabwe.

SUBJECTS

Two hundred and seven lactating women with babies aged 2-12 months.

METHODS

Serum retinol (SR) was measured by HPLC, serum ferritin (SF) by ELIZA, haemoglobin (Hb) by HemoCue and C-reactive protein (CRP) by a turbo metric method. A seven-day recall of consumption of vitamin A containing foods was recorded.

MAIN OUTCOME MEASURES

Relative dose response (RDR), SR, SF, Hb and CRP.

RESULTS

Dark green leafy vegetables were the main sources of vitamin A; retinol-containing foods and yellow to red fruits and vegetables were rarely consumed. Five women had elevated CRP and these women had lower SR (P < 0.001) than the rest. Forty percent of the women had vitamin A deficiency (SR < 20 microg/dl), 76% had low liver stores of vitamin A (RDR > 20%) while 15 women had both abnormal SR and abnormal RDR. Forty percent had anaemia (Hb < 12 g/l) while 12% had iron deficiency (SF < 12 microg/dl) and 4% (n = 7) had iron deficiency anaemia.

CONCLUSION

Vitamin A and iron deficiencies are problems of public health significance among the lactating women in the Makhaza area.

Evaluation of the prototype Roche DNA amplification kit incorporating the new SSK145 and SKCC1B primers in detection of human immunodeficiency virus type 1 DNA in Zimbabwe

We assessed the sensitivity and specificity of a newly developed DNA PCR kit (Roche Diagnostic Corporation, Indianapolis, Ind.) that incorporates primers for all the group M viruses for the detection of human immunodeficiency virus (HIV) type 1 (HIV-1) infection in Zimbabwe. A total of 202 whole-blood samples from adults whose HIV status was known were studied. This included 100 HIV-1-positive and 102 HIV-1-negative samples selected on the basis of concordant results obtained with two enzyme-linked immunosorbent assay kits. The prototype Roche DNA PCR assay had a 100% sensitivity for the detection of HIV-1 DNA and a specificity of 100%. We conclude that the new Roche DNA PCR kit is accurate for the detection of HIV DNA in Zimbabwean samples, in which HIV-1 subtype C dominates.

Retinol-binding protein and asialo-orosomucoid are taken up by different pathways in liver cells

The intracellular transport and degradation of in vivo endocytosed retinol-binding protein was compared with that of asialo-orosomucoid, a marker for receptor-mediated endocytosis through coated pits. The transport pathways were studied in rat liver cells by means of subcellular fractionation in Nycodenz and sucrose density gradients and by immunoelectron microscopy. Retinol-binding protein and asialo-orosomucoid were labeled by covalent attachment of radioiodinated tyramine cellobiose, an adduct which is incapable of crossing cellular membranes and thus provides a marker for the organelles where the protein has been taken up and degraded. The data obtained from subcellular fractionation studies, as well as from immunoelectron microscopy, showed that retinol-binding protein and asialo-orosomucoid were initially localized in different endocytic vesicles. Retinol-binding protein co-localized in density gradients with markers for potocytosis, an alternative endocytic pathway which uses internalization through caveolae instead of clathrin-coated pits. Later, retinol-binding protein and asialo-orosomucoid comigrated in the gradients and they were also observed in the same larger vesicles by immunoelectron microscopy. These data suggest that retinol-binding protein is taken up by liver cells by potocytosis and that a fraction of the retinol-binding protein is later transferred to larger vesicles located deeper in the cytoplasm where degradation takes place.

Tissue distribution of the receptor for plasma retinol-binding protein

The tissue distribution of the retinol-binding-protein receptor has been studied by using a cell-free binding assay. High binding activity was found in placenta, retina pigment epithelial cells, bone marrow and kidneys. Specific binding activity was also found in the small intestines, spleen and liver, and to a lesser extent in lung. Scatchard analysis revealed that the difference in binding activity was due to variations in receptor level and not affinity changes. When the kidneys were separated into cortex and medulla we found that almost all the specific binding activity present in kidneys was recovered in the cortex. The choroid plexus, an important site in the delivery of nutrients to the cerebrospinal fluid, expressed very high binding activity. The pineal gland, which has been shown to store vitamin A, also showed high binding activity. Testes from immature animals showed higher binding activity than testes from mature rabbits. Cultured undifferentiated kidney keratinocytes showed about 40 times higher binding activity than differentiated cells. Skin fibroblasts demonstrated no binding activity. In conclusion, the data presented in this report show that the level of the retinol-binding-protein receptor varies considerably between cell types. The observed tissue distribution of the receptor agrees well with the present knowledge on retinol function and metabolism by various cells.

Transfer of retinol-binding protein from HepG2 human hepatoma cells to cocultured rat stellate cells

Rat liver stellate cells were cocultured with HepG2 human hepatoma cells, which are known to synthesize and secrete retinol-binding protein (RBP). Transfer of human RBP from HepG2 cells to stellate cells was studied by cryoimmunoelectron microscopy. In stellate cells, human RBP was found on the cell surface and within endosomes. The transfer of human RBP from HepG2 cells to stellate cells was blocked by addition of RBP antibodies to the culture medium. Very little uptake of RBP was observed when fibroblasts were cocultured with HepG2 cells. In a series of experiments, RBP was bound to its putative cell surface receptor at 4 degrees C, and the stellate cells were washed and then incubated at 37 degrees C in order to allow them to internalize a pulse of RBP. About 50% of the RBP was internalized after 6 min of incubation. The RBP-positive vesicles were initially (after 1-2 min) located close to the cell surface and later were found deeper in the cytoplasm. During the first 10 min, RBP was mainly observed in close association with membranes. After 2 hr, however, most RBP was localized in intracellular vesicles at a distance from the vesicular membranes, suggesting that RBP had been released from its receptor. Saturable binding of RBP to liver cells was demonstrated when cells were incubated with 125I-RBP at 4 degrees C and cell-associated radioactivity was determined. The calculated dissociation constant for the specific binding was 12.7 +/- 3.2 nM. A binding assay was also developed for determination of solubilized RBP receptor. Solubilized proteins from the nonparenchymal liver cells bound about 30 times more 125I-labeled RBP than did parenchymal cells (based on mass of cell protein). These data suggest that RBP mediates the paracrine transfer of retinol from hepatocytes to perisinusoidal stellate cells in liver and that stellate cells bind and internalize RBP by receptor-mediated endocytosis.

Receptor-mediated endocytosis of retinol-binding protein by liver parenchymal cells: interference by radioactive iodination

Retinol-binding protein (RBP) was iodinated directly by radio-iodine substitution on the tyrosyl residues by the sodium hypochlorite (NaOCl) or the Enzymobead (EB) methods, or indirectly by linkage of 125I-tyramine-cellobiose (TC) or 125I-N-succinimidyl-3-(4- hydroxyphenyl)propionic acid ester (SHPP) adduct on to free amino residues of RBP. Binding, uptake and degradation of iodinated RBP were studied in isolated rat and rabbit liver parenchymal cells. The amount of ligand bound to cells at 4 degrees C was dependent on the type of labelling, in that the 125I-TC ligand was bound to a lesser extent than NaClO-labelled 125I-RBP, EB-labelled 125I-RBP and 125I-SHPP-RBP. At 37 degrees C, the 125I-SHPP-RBP and the EB-labelled 125I-RBP became cell-associated more rapidly than the other two ligands. The higher cell association at 37 degrees C than at 4 degrees C suggests that internalization of the ligand occurred at the higher temperature. The degradation of the ligands was also different. The EB-labelled 125I-RBP, the 125I-TC-RBP and the 125I-SHPP-RBP showed an apparent lag phase before a steady increase in acid-soluble radioactivity was observed. Much less of EB-labelled 125I-RBP and 125I-TC-RBP were degraded (about 6%) than of the other two ligands (about 16%) after 120 min. About 50% of the acid-soluble radioactivity in these experiments could be accounted for by degradation in the medium, suggesting that about half of the degradation observed was intracellular. The present study therefore shows that the different labelling techniques yield varying estimates of the cellular handling of RBP. In addition, a rapid release of RBP was observed in experiments where cells were pulsed with radioactive RBP at 4 degrees C, washed and incubated further at 37 degrees C. Between 50% and 70% was released after 5 min of incubation. By increasing the temperature during the pulse to 37 degrees C, or by lowering the temperature during the chase to 4 degrees C, much less RBP was released from the cells. These data suggest that the release process represents recycling of internalized ligand from an early endosome.