Difference between C3H mice and Wistar rats in the effect of external gamma-irradiation on 59Fe release from alveolar macrophage-ingested 59Fe-iron hydroxide colloid.

The effect of external gamma-irradiation on 59Fe release from alveolar macrophages (AMs) that had ingested 59Fe-iron hydroxide colloid was determined in C3H mice and Wistar rats with an in vitro assay system. The release of 59Fe from AM was increased by irradiation in mice but not in rats. A significant increase in 59Fe release was seen in mouse AM cultured for 72 hrs after irradiation at a dose of more than 25 Gy; but, graded doses of gamma-irradiation up to 100 Gy had no effect on 59Fe release from rat AMs. This difference between mice and rats may be attributable to the magnitude of death of or damage to AM because the survival of AMs assessed by vital staining with crystal violet decreased much more in mice than in rats.     

Durability of man-made vitreous fibres as assessed by dissolution of silicon,iron and aluminium in rat alveolar macrophages

The dissolution of man-made vitreous fibres (MMVF) by rat alveolar macrophages (AM) was studied in vitro. The fibre samples included refractory ceramic (RCF 1–4), glasswool (MMVF 10, 11), rockwool (MMVF 21) and slagwool fibres (MMVF 22). Experimental fibre REC 1 of calcium silicate type served as an internal control fibre. The fibres were incubated with cultured rat AM or in mere cell-culture medium for 2, 4 or 8 days. The dissolution of the fibres was determined by measuring the amount of silicon (Si), iron (Fe) and aluminium (Al) in the medium with or without rat AM. Si was markedly dissolved only from the glasswool fibres (MMVF 10 and 11) and from the experimental fibre REC 1. Fe was dissolved, in turn, more from rockwool fibres than from the other fibres. Al was effectively dissolved from the ceramic fibres (RCF) 1–3. The dissolution of Fe and Al from the fibres was effective in the presence of AM, whereas the dissolution of Si was greater in the mere culture medium. The results of present study suggest that glasswool fibres (MMVF 10 and 11) are dissolved more readily in mere culture medium where the pH is close to neutral, whereas rockwool fibres are sensitive to the effects of more acidic milieu in AM culture.     

Radioprotection of normal tissues in tumor-bearing mice by troxerutin

The flavanoid derivative troxerutin, used clinically for treating venous disorders, protected biomembranes and cellular DNA against the deleterious effects of gamma-radiation. The peroxidation of lipids (measured as thiobarbituric acid-reacting substances, or TBARS) in rat liver microsomal and mitochondrial membranes resulting from gamma-irradiation up to doses of 500 Gy in vitro was prevented by 0.2 mM troxerutin. The administration of troxerutin (175 mg/kg body weight) to tumor-bearing mice by ip one hour prior to 4 Gy whole-body gamma-irradiation significantly decreased the radiation-induced peroxidation of lipids in tissues such as liver and spleen, but there was no reduction of lipid peroxidation in tumor. The effect of troxerutin in gamma-radiation-induced DNA strand breaks in different tissues of tumor-bearing mice was studied by comet assay. The administration of troxerutin to tumor-bearing animals protected cellular DNA against radiation-induced strand breaks. This was evidenced from decreases in comet tail length, tail moment, and percent of DNA in the tails in cells of normal tissues such as blood leukocytes and bone marrow, and these parameters were not altered in cells of fibrosarcoma tumor. The results revealed that troxerutin could preferentially protect normal tissues against radiation-induced damages in tumor-bearing animals.     

The retention of 59Fe and 65Zn by preruminant lambs given milk-substitutes based on either casein or soya-bean-protein isolate

Eight newborn lambs were given milk-substitutes based on casein (n 4) or a soya-bean-protein isolate (n 4). On the morning before a 10 d collection period, the milk-substitutes were supplemented with 59Fe as ferric chloride and 65Zn as zinc chloride. Faeces and urine were collected daily and determinations of 59Fe and 65Zn were made on these separately. During a second 10 d period the dosing procedure and collection were repeated but the diet of each lamb was reversed. Mean retention of 59Fe in lambs given the casein diet was 0.50 (SE 0.12) and in those given the soya-bean-protein diet 0.06 (SE 0.05). There were large variations among animals but the treatment effect was significant at P less than 0.05. Retention of 65Zn was significantly greater than that of 59Fe for all lambs but the effect of dietary treatment was similar to that for Fe. 65Zn retention values for casein and soya-bean-protein diets were 0.84 (SE 0.06) and 0.52 (SE 0.03) respectively, and the difference was significant at P less than 0.01. There were only very small amounts of 59Fe and 65Zn in urine, representing 0.002-0.003 of the dose.     

The effect of different levels of wheat bran on iron absorption in rats from bread containing similar amounts of phytate

1. Iron absorption was studied in weanling rats using balance techniques from semi-synthetic diets containing dried white bread (60.5 g dietary fibre/kg. White & Southgate, unpublished results), brown bread (130.2 g dietary fibre/kg) or wholemeal bread (221.2 g dietary fibre/kg) at a level of 300 g/kg and compared with a control group given a diet containing added FeSO4 at a similar Fe level to that for the bread groups. The dried bread contained 6.2-6.4 g phytate/kg. 2. Absorption of Fe was significantly higher (P less than 0.001) in the control group (0.45) than in the White (0.28), brown (0.31) or wholemeal (0.24) groups. 3. A second experiment was carried out on 6-week-old rats in which the dried bread was extrinsically labelled with 59Fe and absorption from a single meal measured by both faecal excretion and incorporation of 59Fe into the blood. Control animals were given 59FeSO4 for comparison. 4. The excretion of 59Fe (% of administered dose) was significantly lower (P less than 0.001) in the control group (31) than in the white (48), brown (45) or wholemeal (47) groups. After 10 d the control group had significantly more 59Fe in the blood than the bread groups, but there were no differences between the bread groups. 5. It appears that wheat bran fibre itself has no effect on the retention of Fe from the diet in the rat, when supplied in amounts similar to those found in commercially-available bread.     

Iron and zinc concentrations and 59Fe retention in developing fetuses of zinc-deficient rats

Because disturbances in iron metabolism might contribute to the teratogenicity of zinc deficiency, we examined the effect of zinc deficiency on fetal iron accumulation and maternal and fetal retention of 59Fe. Pregnant rats were fed from mating a purified diet containing 0.5, 4.5 or 100 micrograms Zn/g. Laparotomies were performed on d 12, 16, 19 and 21 of gestation. Maternal blood and concepti were analyzed for zinc and iron. Additional groups of dams fed 0.5 or 100 micrograms Zn/g diet were gavaged on d 19 with a diet containing 59Fe. Six hours later maternal blood and tissues, fetuses and placentas were counted for 59Fe. Maternal plasma zinc, but not iron, concentration was affected by zinc deficiency on d 12. Embryo zinc concentration on d 12 increased with increasing maternal dietary zinc, whereas iron concentration was not different among groups. On d 16-21 plasma iron was higher in dams fed 0.5 micrograms Zn/g diet than in those fed 4.5 or 100 micrograms/g, whereas plasma zinc was lower in dams fed 0.5 or 4.5 micrograms Zn/g than in those fed 100 micrograms Zn/g diet. On d 19 zinc concentration in fetuses from dams fed 0.5 micrograms/g zinc was not different from that of those fed 4.5 micrograms/g zinc, and iron concentration was higher in the 0.5 microgram Zn/g diet group. The increase in iron concentration in zinc-deficient fetuses thus occurs too late to be involved in major structural teratogenesis. Although whole blood concentration of 59Fe was not different in zinc-deficient and control dams, zinc-deficient dams had more 59Fe in the plasma fraction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Measurement of non-haem iron absorption in non-anaemic rats using 59Fe: can the Fe content of duodenal mucosal cells cause lumen or mucosal radioisotope dilution, or both, thus resulting in the underestimation of Fe absorption?

Male Wistar rats (188 g) were fed on a semi-synthetic (SS) diet (38 mg iron/kg) ad lib. for 7 d and then meal-fed for 1 d. After a 21 h fast each rat was given one meal (10 g) of high-Fe SS (500 mg Fe/kg; high-Fe group) or control (38 mg Fe/kg; control group) diet. After 16 h 2 ml of an 59Fe-labelled ferrous sulphate solution (18 kBq 59Fe; 120 micrograms Fe) was administrated by gavage and equal numbers of rats from each group were killed 6 or 24 h after dosing. Mucosal uptake of 59Fe from the gut lumen and transfer of 59Fe from mucosa into the carcass were measured. Total Fe content of the duodenum was also determined. Mucosal 59Fe uptake and transfer were markedly lower in the high-Fe group compared with the control group. The Fe content of the duodenum, the major region of Fe absorption, was significantly greater in the high-Fe group than in the controls. A larger amount of Fe may thus have been released into the lumen of the high-Fe rats, via mucosal cell turnover, resulting in a greater lumen dilution of the 59Fe dose in this group compared with the controls. Calculations are presented which demonstrate that such an effect could not possibly account for the observed difference in mucosal 59Fe uptake between groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of dietary iron deficiency and tungsten supplementation on 59Fe absorption and gastric retention from 59Fe compounds in rats

1. In vivo 59Fe absorption from intrinsically labelled Fe-containing fractions of liver and blood were measured in rats by intragastric dosing. All rats were fed on a low-Fe diet for 3 d before dosing in order to standardize the Fe status of the intestinal mucosal cells. 2. An increase in digestion time from 2 to 12 h increased 59Fe absorption (P less than 0.01) from all fractions except ferritin. 3. Fe-deficient rats when compared with essentially Fe-replete rats showed decreased gastric retention for all fractions, but increased 59Fe absorption over 2 h only from ferritin. Ferritin showed several unusual absorption characteristics. 4. Dietary tungsten supplementation of Fe-deficient rats reduced the ferroxidase activity of intestinal mucosal xanthine oxidase. In addition, gastric retention and 59Fe absorption (P less than 0.05) from all fractions were increased.     

Effect of soya-bean protein on meat iron solubility and absorption in rats

1. Soya-bean proteins were used to replace 30 and 50% of the protein from 59Fe-labelled pigeon (Columba L.) and chicken meat, and the solubility of the meat 59Fe in vitro and its absorption in vivo in rats in the presence and absence of soya-bean proteins were measured. 2. Replacement of part of the chicken meat by soya-bean proteins reduced 59Fe solubility from chicken meat at all stages during simulated in vitro digestion. 3. 59Fe absorption from 59Fe-labelled chicken meat when given to both Fe-replete and Fe-deficient rats was reduced in the presence of soya-bean proteins but was unaffected by the presence of casein or bovine serum albumin. 59Fe-absorption from pigeon meat in the presence of soya-bean proteins was not reduced to the same extent as that from chicken meat. 4. There was no significant effect of soya-bean proteins on 59Fe-labelled haemoglobin Fe absorption in vivo in Fe-replete rats. 5. Absorption of 59Fe from the isolated haemoproteins from chicken meat was unaffected by soya-bean proteins but 59Fe absorption from the main non-haem-Fe fractions was strongly inhibited, particularly from haemosiderin.     

The effect of differences in dietary iron intake on 59Fe absorption and duodenal morphology in pregnant rats

The effect of iron intake on 59Fe absorption throughout pregnancy, and on maternal and fetal Fe status towards the end of pregnancy, was investigated in rats. The influence of pregnancy and dietary Fe on duodenal morphology was also studied. Female rats were fed on a diet containing 17 or 100 mg Fe/kg for 2 weeks before and throughout pregnancy. 59Fe absorption was measured on days 1 or 2, 8 or 9 and 17 or 18 of pregnancy, and maternal and fetal Fe status was determined on days 18 or 19. Pregnancy resulted in a fall in haemoglobin (Hb) concentration. Compared with non-pregnant counterparts, total liver Fe was reduced in the low-Fe group, but not in the high-Fe group, indicating that the fall in Hb in the high-Fe rats was not associated with an Fe-deficient state. 59Fe absorption in rats fed on both diets increased throughout pregnancy, demonstrating that Fe supplementation of the diet, to a level that prevented the development of Fe-deficiency, failed to suppress an increase in absorption. Fetal weight appeared to be an important determinant of the efficiency of Fe absorption in late pregnancy. Poor maternal Fe status was accompanied by a reduction in fetal Fe concentration but results also suggested that fetuses were partly protected from maternal Fe-deficiency. Pregnancy resulted in increased duodenal circumference and villus dimensions, whilst high dietary Fe reduced duodenal growth in both pregnant and non-pregnant animals. The relevance of this finding is discussed. It was concluded that, in rats, pregnancy per se causes an enhancement in Fe absorption and that the degree of enhancement is in part related to fetal mass.     

Influence of fish on the bioavailability of plant iron in the anemic rat

The effect of fish protein and fish oil on the utilization of endogenous iron in wheat bran, spinach and soy protein isolate was investigated by using the anemic rat as an animal model. Marine products were substituted for casein and corn oil in the diets of these animals. Hemoglobin regeneration was one criteria used to measure iron uptake. Relative biological values (RBV) were computed from a regression equation obtained from control animals receiving graded levels of FeSO4 X 7H2O. The RBV of iron from plant sources provided in diets containing casein-corn oil versus fish-fish oil were: wheat bran, 123 vs. 111%; spinach, 53 vs. 49%; and soybean isolate, 84 vs. 67%; RBV FeSO4 = 100%. These changes were not significant. The decreases in iron absorption from diets containing marine products was attributed to the fish oil. Absorption of exogenous iron (59Fe) was measured in the same animals after the 14-day repletion period. Assimilation of the 59Fe was highly correlated (r2 = 0.958) with hemoglobin level at time of dosing. Diet composition did not appear to have the same effect on the percentage of 59Fe retained after 110 hours by the rat as compared to levels of hemoglobin regeneration (i.e., RBV). A "meat factor" effect was not shown by substituting fish for casein the diets containing plant iron sources fed anemic rats.     

Studies on the roles of apotransferrin and caeruloplasmin (EC 1.16.3.1) on iron absorption in copper-deficient rats using an isolated vascularly- and luminally-perfused intestinal preparation

1. Studies have been made on the effects of dietary copper on the iron and Cu distribution in rats and on the metabolic activity and absorptive capacity of intestines perfused both vascularly and luminally. 2. Rats maintained for 4-5 weeks on a Cu-deficient diet (0.4 microgram Cu/kg) had significantly lower plasma, liver and intestinal Cu concentrations and significantly reduced plasma caeruloplasmin and liver cytochrome c oxidase (EC 1.9.3.1) activity compared with controls receiving a Cu-supplemented diet (5 micrograms Cu/kg). Disturbances in Fe metabolism in Cu-deficient rats were evident as shown by a mild anaemia, significantly elevated hepatic Fe concentrations and hypoferraemia. 3. Intestinal glucose uptake from both the luminal perfusion medium (LPM) and vascular perfusion medium (VPM) was unaffected by Cu deficiency despite a significant (25-30%) reduction in oxygen consumption. This was associated with a 40% decline in mucosal cytochrome c oxidase activity. 4. In studies of Fe absorption, Fe uptake from the LPM was unaffected by Cu deficiency while transfer of Fe to VPM was significantly reduced (50%) compared with control preparations. Addition of apotransferrin (1 g/l) to the VPM was without effect in preparations from control rats but significantly increased the transfer of Fe to the VPM in preparations from Cu-deficient rats without affecting Fe uptake from the LPM. 5. The addition of either human or porcine caeruloplasmin (together with apotransferrin) to the VPM, such that the resultant ferroxidase (EC 1.16.3.1) activity of the VPM supernatant fraction was four to five times that of normal rat plasma, was without effect on either Fe uptake, tissue retention or Fe transfer to the VPM by preparations from either Cu-deficient or control rats. 6. These findings offer no evidence in support of the proposed role for caeruloplasmin with its associated ferroxidase activity in Fe absorption in the rat.     

可乐定置换物对正常大鼠离体胰岛功能的影响

目的 探讨可乐定置换物(CDS)对离体正常大鼠胰岛功能的影响。方法 胶原酶和DNA酶联合消化法分离SD大鼠胰岛，RPMI1640组织培养液过夜培养，采用Millipore Multisereen系统观察CDS对胰岛功能的影响。放免法测定孵育液中胰岛素及胰高糖素的浓度。结果 离体胰岛胰高糖素的分泌明显受葡萄糖浓度的抑制，CDS显著抑制胰高糖素的分泌，且抑制强度明显依赖于CDS的浓度。离体胰岛胰岛素的分泌依赖于孵育液中的葡萄糖浓度，CDS明显刺激胰岛素的释放。Ca^2 通道阻滞剂硝苯吡啶(25μmol／L)及K^ 通道开放剂二氮嗪(100μmol／L)可显著抑制胰岛素释放，但其作用可被CDS消除。结论 作为咪唑啉受体的内源性配体，CDS可刺激离体胰岛胰岛素的释放，抑制胰高糖素的分泌。     

The effect of diet on retention by the rat of iron from a radiolabeled casein test meal

Previous work has shown that weanling rats fed a soy protein isolate (SPI)-based diet retained less iron from a casein test meal than did rats fed a casein-based diet. In the present work this diet effect was further investigated. In experiment 1 rats were fed either SPI-or casein-based diet (about 25 ppm Fe) for 13 d, fasted overnight, given a 59Fe-labeled casein-based test meal, and refed either the same or the other diet for 7 d. 59Fe retention was determined by the percent of ingested label retained after 7 d. SPI reduced 59Fe retention when fed prior to the test meal (52.5 vs. 61.5%, P less than 0.001) and also when fed following the test meal (50.8 vs. 63.2%, P less than 0.001). In experiment 2a, exposure of SPI to steam at 108 degrees C for 30 min did not lessen the observed diet effect. In experiment 2b rats were fed either an SPI-or casein-based diet, and casein test meals were fed as above on days 14, 35 and 56. The SPI-based diet reduced 59Fe retention from the casein test meal fed on d 14 (58.2 vs. 68.0%, P less than 0.005), for the meal on d 35 there was no difference, and for the final test meal rats fed SPI retained more 59Fe (53.0 vs. 40.2%, P less than 0.01). In experiment 3 lactalbumin was shown to decrease 59Fe retention to the same extent as SPI (54.9 and 53.4%) as compared to casein (73.3%), whereas neither rapeseed protein concentrate (68.8%) nor oxalic acid (72.2%) had any significant adverse effect.(ABSTRACT TRUNCATED AT 250 WORDS)     

Phagocytosis of alveolar macrophages of pyridoxine-deficient rats

We measured phagocytosis of opsonized sheep red blood cells by alveolar macrophages (AM) of rats fed a diet with or without pyridoxine for 4 weeks. In pyridoxine-deficient (DEF) and pair-fed control (PF) groups AM showed a higher degree of phagocytosis than those of rats in the ad libitum-fed control (AL) group. After in vitro treatment with a macrophage-activating factor (MAF), such as lymphokines, for 4 hours at 37 degrees C, AM from the PF and AL groups showed a greater enhancement of phagocytic activity than AM from the DEF group, which was slightly enhanced. When the effect of MAF prepared from splenic cells of rats of the PF or DEF groups on the phagocytosis of AM was observed, MAF from the PF group showed an approximate 35% increase of phagocytic ability compared to the supernatant of splenic cells cultured with medium only. However, MAF from the DEF group had no effect on phagocytosis. These results suggest that pyridoxine deficiency affects not only phagocytic function of AM responsible for host defense in the lung but also MAF production by splenic cells.     

低剂量中子辐射对大鼠肾组织细胞外基质成分表达的影响

目的 研究低剂量中子辐射对大鼠肾组织细胞表达细胞外基质成分的影响。方法 大鼠随机分4组,分别接受不同剂量的中子照射后,取肾组织用胶原酶消化以分散细胞,采用放射免疫方法测定原代培养细胞上清中的细胞外基质成分的含量。结果 0.29 Gy和1.21 Gy的中子对HA和PC Ⅲ的影响不明显,但都显著刺激LN的增加;0.62 Gy的中子可显著抑制HA和PC Ⅲ,对LN的影响却不明显。中子对三种基质成分影响的量效规律有着一致性,均表现为中剂量(0.62 Gy)组的测定值比低剂量组和高剂量组的测定值低。结论 低剂量中子辐射可引起大鼠肾组织细胞分泌细胞外基质成分发生变化。     

Studies of iron:zinc interactions in adult rats and the effect of iron fortification of two commercial infant weaning products on iron and zinc status of weanling rats

The effect of iron on zinc absorption in the rat, and vice versa, was investigated from single starch:sucrose test meals (containing 65Zn or 59Fe) by whole body counting. Zinc had no effect on iron absorption, but iron reduced zinc absorption when the total ionic species in the meal (iron plus zinc) reached 1.36 mg. Below this level, high iron:zinc molar ratios (10:1) had no effect on zinc absorption, presumably because the transport mechanism for zinc had not reached full capacity. Previous iron intake had no effect on zinc absorption. The relevance of these findings to infant foods was explored by feeding rats exclusively a vegetable or cereal weaning product, with or without additional iron, for 12 d and measuring zinc and iron status. The added iron raised body iron stores and caused a small reduction in zinc status in animals fed the oat, but not the vegetable, diet as measured by plasma and femur zinc concentrations. Since the threshold level of 1.36 mg ionic species would be exceeded when the animal ate 3-4 g of the iron-fortified weaning food at any one time, it appears that the iron:zinc interactive effect was absent in the vegetable and less potent in the oat formulation than in a carbohydrate test meal. Alternatively, it may be the case that the animals had responded over time to reduced zinc availability by increasing whole body zinc retention.(ABSTRACT TRUNCATED AT 250 WORDS)     

Factors affecting the absorption of iron from Fe(III)EDTA

1. The modification of iron absorption from Fe(III)EDTA by agents known to promote or inhibit absorption was examined in 101 volunteer multiparous Indian women. Fe absorption from Fe(III)EDTA was compared with absorption of intrinsic food Fe in a further twenty-eight subjects. Finally the urinary excretion of radio-Fe after oral administration of 59Fe(III)EDTA was studied in twenty-four subjects and evidence of intraluminal exchange of Fe was examined. 2. Fe absorption from maize porridge fortified with Fe(III)EDTA was more than twice that from porridge fortified with FeSO4 . 7H2O. 3. Although bran decreased Fe absorption from FeSO4 . 7H2O approximately 11-fold, it had no significant effect on Fe absorption from Fe(III)EDTA. Nevertheless tea, which is a more potent inhibitor of Fe absorption, decreased absorption from Fe(III)EDTA 7-fold. 4. Fe absorption from Fe(III)EDTA given in water was only increased 40% by addition of 3 mol ascorbic acid/mol Fe but by 7-fold when the relative proportions were increased to 6:1. This enhancing effect was blunted when the Fe(III)EDTA was given with maize porridge. In these circumstances, an ascorbate:iron value of 3:1 (which doubles absorption from FeSO4 . 7H2O) produced no significant increase in Fe absorption, while a value of 6:1 produced only a 2 . 5-fold increase. 5. Fe absorption from Fe(III)EDTA was not altered by addition of maize porridge unless ascorbic acid was present. 6. Less than 1% of 59Fe administered as 59Fe(III)EDTA was excreted in the urine and there was no inverse relationship between Fe absorption and the amounts excreted (r 0 . 58, P less than 0 . 05). 7. Isotope exchange between 59Fe(III)EDTA and 59FeSO4 . 7H2O was demonstrated by finding a similar relative value for the two isotopes in urine and erythrocytes when the two labelled compounds were given together orally. This finding was confirmed by in vitro studies, which showed enhanced 59Fe solubilization from 59FeSO4 . 7H2O in maize porridge when unlabelled Fe(III)EDTA was added. 8. Although Fe absorption from Fe(III)EDTA was marginally higher it appeared to form a common pool with intrinsic food iron in most studies. It is postulated that the mechanism whereby Fe(III)EDTA forms a common pool with intrinsic food Fe differs from that occurring with simple Fe salts. When Fe is present in the chelated form it remains in solution and is relatively well absorbed because it is protected from inhibitory ligands. Simple Fe salts, however, are not similarly protected and are absorbed as poorly as the intrinsic food Fe. 9. It is concluded that Fe(III)EDTA may be a useful compound for food fortification of cereals because the Fe is well absorbed and utilized for haemoglobin synthesis. The substances in cereals which inhibit absorption of simple Fe salts do not appear to inhibit absorption of Fe from Fe(III)EDTA.     

Evaluation of uncertainties in estimates of fetal doses from 59Fe kinetic studies at Vanderbilt University

In a 1997 paper, Stabin et al. published estimates of the fetal radiation doses for women who received oral administrations of 59Fe at Vanderbilt University in the 1940's. These authors concluded that there was "considerable uncertainty... in the amount of radioactive material administered to these subjects." In an effort to quantify this uncertainty, the underlying factors in the input data used in the Stabin et al. dose estimates have been examined in detail. Such factors include (a) an absence of detailed information on, and discrepancies in, the amounts of 59Fe reported to have been administered; (b) the probability that the radioactive iron included 55Fe as well as 59Fe; (c) uncertainties as to the period of time that elapsed between the administration of the radioiron and the taking of the maternal blood samples, and the accompanying impacts of radioactive decay; (d) possible losses of 59Fe in the procedures used in preparing the blood samples; and (e) questions as to the reported efficiency of the counting equipment. Our principal conclusion is that, due to the significant uncertainties and the lack of key information, it is not possible to estimate the doses accurately. An ancillary conclusion, however, is that the doses were probably significantly higher than previously estimated. This latter possibility should be carefully considered by any investigators who subsequently seek to use these estimates to quantify the relationship between the doses to the fetus and the resulting health effects.     

The effect of three types of saponin on iron and zinc absorption from a single meal in the rat

1. Iron and zinc retentions in young male rats, given 3 g starch-sucrose paste containing 120 micrograms Fe as FeSO4 or 139 micrograms Zn as ZnCl2 (extrinsically labelled with 59Fe or 65Zn) and increasing amounts of Gypsophila saponins, were measured by whole-body counting. The results were compared with whole-body Fe and Zn retention from a meal containing crude or purified saponin fractions. In a separate experiment Fe retention from a meal containing Gypsophila saponins, soyasaponin I, or saponins extracted from lucerne (Medicago sativa) plant tops, was measured in older rats. 2. Results indicated that Fe absorption decreased with increasing concentration of Gypsophila saponins. This was significant at a saponin:Fe molar value of approximately 1, with maximum effect occurring at molar ratios of 4 and above, when Fe absorption was reduced by approximately 17%. Gypsophila saponins had no effect on Zn absorption from a test meal. 3. Fe absorption was similar in groups given purified or crude Gypsophila saponins at the same saponin:mineral molar value of 8, demonstrating that the 'non-saponin' fraction of the commercial preparation does not affect the absorption of this mineral. 4. Saponins extracted from lucerne plant tops, fed at a saponin:Fe value of approximately 8, also reduced Fe absorption from a single meal. Fe absorption from a meal containing a similar amount of soyasaponin I was not significantly different from controls. 5. These results indicate that some dietary saponins may reduce Fe absorption and hence have an adverse effect on Fe status in man and simple-stomached animals.