Kinetics of lead retention and distribution in suckling and adult rats

The kinetics of lead distribution was studied in suckling and adult rats 8 days after a single intraperitoneal injection of ²⁰³Pb. Marked differences were observed in the kinetics of lead retention and distribution in suckling as compared to adult rats. The rate of ²⁰³Pb disappearance was lower in the whole body, blood and kidneys, but higher in the liver, while the deposition processes predominated in the brain, femur and teeth of sucklings as compared to adult animals.     

The effects of dietary lead content and food restriction on lead retention in rats

The effects of restricted food intake and of various dietary lead contents on lead retention¹ were studied in young rats. In three experiments the rats were given either unrestricted or restricted access to diets providing 200 or 400 mg lead/kg for 3 or 6 weeks. At the end of the experiments a sample of blood was taken and the rats were ashed. Lead was determined in blood and ash from the carcass. Food restriction always increased the retention of lead but not always the lead content of blood or carcass. The retention of lead was similar when the diet was supplemented with 50, 200 or 400 mg lead/kg. Lead supplementation at 200 or 400 mg/kg reduced food intake and growth but did not affect food conversion ratios. Blood lead was related to the rate of ingestion of lead. The effect of food restriction in reducing lead retention should be taken into account in interpreting the effects of lead exposure accompanied by dietary conditions which reduce appetite or food supply.     

Lower efficiency of DTPA in reducing cadmium retention in suckling rats

The influence of age on the effectiveness of chelation therapy in enhancing cadmium elimination was studied in 1-, 2-, 8-, and 26-week-old rats. 115mCd was administered intraperitoneally, followed immediately and after 24 hr by an intraperitoneal injection of trisodium calcium diethylenetriaminepentaacetate (DTPA) (600 mumole/kg body wt). The whole body retention determined on the second, fourth, and sixth days of the experiment showed that DTPA greatly decreased cadmium retention in all age groups being about four times more effective in older than younger animals. Determination of 115mCd retention in the gut and organs also revealed that effectiveness of DTPA was lowest for the youngest age group and increased with increasing age. This effect of DTPA was more pronounced in the liver than in the kidney and brain in all age groups. These results indicate that age greatly influences chelation of cadmium and that age might be an important factor in chelation therapy in general.     

Effect of carbohydrates on lead absorption and retention in weanling rats

This study was designed to determine the effect of corn starch, lactose, and sucrose on lead (Pb) absorption and retention in rat tissues and organs. Seventy weanling Wistar male rats were assigned to the following five treatment groups: Group 1, 31.2% sucrose + 29.3% starch; Group 2, 31.2% lactose + 29.3% starch; Group 3, 60% corn starch (control); Group 4, 52.1% sucrose + 8.4% starch; Group 5, 52.1% lactose + 8.4% starch. All diets were supplemented with 200 ppm lead nitrate. The animals were fed the experimental diets for 8 weeks after which they were sacrificed. Analysis of lead in whole blood, bone (tibia and femur), carcass ash, and gut (alimentary canal) was done by atomic absorption spectrophotometric (AAS) technique. Results indicated that lactose in the diet caused increased lead retention by these tissues. Pb concentration was highest in blood (500% of the control) and bone (433% of control) of animals fed the Group 5 diet with the second highest level for the tissues of rats fed the Group 2 diet. Rats fed the high lactose diet showed the lowest weight gain and those fed the low sucrose diet showed the highest weight gain. The sucrose diets caused increased Pb in bone. In rats fed the sucrose diets, the Pb content of feces was greater than the value in rats fed the corn starch diet. The results of this study show that lactose has a higher stimulatory effect on Pb retention than sucrose.     

The effect of milk diet on lead metabolism in rats

The effect of milk on lead absorption and retention was studied in four groups of 6-wk-old female rats after a single oral or intraperitoneal application of lead-203. The animals were fed different diets for 2 wk (1 wk prior and 1 wk after the radiolead application). All animals receiving milk diet or milk additives showed a higher intake of fats and proteins and a lower intake of carbohydrates, vitamin D, and iron than control rats fed on normal diet. The calcium, phosphate, and calorie intake was about the same in all groups.The body retention of the orally applied lead-203 was much higher in animals on milk diet (4 times higher in rats on normal diet and cow's milk; 57 in animals on cow's milk; 33 times in rats on powdered milk) than in controls. The milk diet had only a slight effect on the whole body retention of lead-203 after intraperitoneal application (1.3 and 1.2 times higher in rats on cow's and powdered milk, respectively).This indicates that milk causes considerable enhancement of lead retention in the body mainly by greatly increasing its absorption from the intestinal tract.     

The effect of dietary supplementation with calcium salts on skeletal calcium in suckling rats

This study aimed at identifying a calcium compound which could serve as an effective and safe dietary supplement in suckling rats over the period of intense growth and development. The main objective was to assess the effect of additional calcium intake on skeletal calcium in suckling pups. Suckling Wistar rats were fed using a pipettor with one of the following calcium salts from day 6 to 14 after the birth: gluconate, hydrogenphosphate, carbonate (each suspended in cow's milk), or chloride (in demineralized water). Control rats received only cow's milk. Calcium in the carcass (body without organs and skin) was analysed by atomic absorption spectrometry. The only effective dietary supplement that produced no risk for the suckling pups' growth was calcium hydrogenphosphate in cow's milk in the total amount of 340 mg. That dose increased the daily calcium intake 3 to 4 times compared to non-supplemented controls, increasing carcass calcium content by about 16 per cent. Other calcium compounds were either inefficient (carbonate) or had adverse effects on pups' growth (chloride and gluconate).     

Effect of maternal zinc supply on blood and tissue metallothionein I concentrations in suckling rats

Changes in metallothionein I (MT-I) levels were measured in blood and tissues of rat pups from dams given diets containing 6, 9 or 40 mg zinc/kg from wk 1 or gestation and throughout lactation. After 1, 2 and 3 wk of lactation, litters from each group were killed and tissues analyzed for MT-I. The relatively mild degree of zinc deficiency, which had no effect on fetal viability or litter size and caused only slightly lower pup weight, caused significantly lower MT-I concentrations in pup liver, thymus, plasma and red cells, particularly in pups from dams receiving 6 mg zinc/kg. Maternal zinc supply is therefore a major determinant of MT-I concentrations in neonatal tissues, and assay of this protein in blood plasma and red cells may give a useful indication of zinc status.     

Influence of maternal magnesium deficiency on tissue lead content of rats

Diets containing 150 or 600 ppm magnesium with or without 200 ppm lead were fed to rats throughout gestation and lactation to determine the influence of moderate magnesium deficiency on tissue lead content of maternal and offspring tissue. During lactation it was necessary to increase the lowest dietary magnesium level to 225 ppm. Lead caused a significant depression in both gestational weight gain and average pup weight regardless of the level of dietary magnesium. Maternal magnesium deficiency was evidenced by significant reductions in serum and tibia magnesium, a 17-fold increase in kidney calcium, and hyperemia of the ears. In offspring, however, only growth and tibia magnesium were significantly affected by the magnesium deficiency, and the maternal-fetal difference in serum and tibia magnesium concentration was maintained. Maternal magnesium deficiency resulted in significantly higher lead concentrations in dam liver, and offspring erythrocytes, liver and tibia. A mechanism for the enhanced accumulation of lead in maternal and offspring tissue as a result of maternal magnesium deficiency is not defined, but it is likely to involve enhanced intestinal lead absorption.     

The effects of dietary calcium and phosphorus on the retention and excretion of lead in rats.

1. Rats were given diets containing different amounts of calcium, phosphorus and lead. 2. Pb retention was greatly increased when the diets contained less Ca or P than the minimum estimated requirement of the rat. 3. The release of Pb already incorporated into the skeleton was inhibited by diets low in Ca but was not affected by diets low in P. 4. The retention of Pb given intraperitoneally was not affected by dietary Ca or P. 5. It can be concluded that dietary Ca and P influence the absorption of Pb by the gut and dietary Ca influences the metabolism of Pb in the bone. 6. There were changes in the distribution of Pb among the tissues due to changes of dietary Ca. 7. At low body concentrations, Pb probably affected skeletal growth.     

Iron status of suckling rats as influenced by maternal diet during gestation and lactation

1. Two experiments are reported. In Expt 1, pregnant Sprague-Dawley rats (200-220 g) were given purified diets containing 35, 75, 150 or 300 mg Fe/kg throughout gestation and lactation. In Expt 2, the levels of Fe given were 250 and 300 mg/kg diet. 2. Litters were standardized at birth to contain seven pups. On day 20 of lactation blood, milk, spleen and liver were collected for Fe analysis. 3. A dietary Fe concentration of 35 mg/kg maintained maximum weight gain, food intake, liver and spleen weight, haemoglobin concentration and packed cell volume in the growing maternal rat through 20 d of lactation. Dam liver and spleen Fe concentrations were maximized between 75 and 250 mg Fe/kg diet. 4. Pups (20-d-old) nursed by dams given 35 mg Fe/kg tended to have lower body and organ weights compared to other groups. Liver and spleen Fe concentrations increased with increasing maternal dietary Fe and were significantly increased between 150 and 250 mg Fe/kg.     

The effect of cellulose and glucomannan on the absorption of lead in rats]

The effect of two different fibers on lead (Pb) absorption was investigated during two 3-day balance-study periods (day 15th to 17th and 30th to 32nd) of a 32-day feeding course in young rats. Young rats were fed for 32 days diets containing Pb (200 mg/kg diet), with or without the addition of 10% cellulose or glucomannan. The following results were obtained: 1) The total fecal Pb content was significantly increased (p less than 0.05) in the Pb + cellulose group than in the Pb alone group during both balance-study periods. However, there was no significant difference between the Pb alone group and the Pb + glucomannan group. 2) Lead retention was significantly lower (p less than 0.05) in the Pb + cellulose group than in the Pb alone group during both balance-study periods. However, there was no significant difference observed between the Pb alone group and the Pb + glucomannan group. 3) Rats fed on the Pb + glucomannan diet had a significantly heavier (p less than 0.05) cecum and large intestine than rats fed on the other two diets. 4) The concentration of Pb in the cecum was significantly lower (p less than 0.05) in the Pb + cellulose group than in the other two groups. These results indicate that cellulose supplementation reduced the retention of Pb, while glucomannan supplementation had no significant effect on the retention of Pb.     

Effect of vitamin D and low dietary calcium on lead uptake and retention in rats

The effects of cholecalciferol (formerly vitamin D-3) supplementation and alterations in dietary calcium levels on intestinal 210Pb absorption and tissue uptake were studied in weanling female Sprague-Dawley rats. Rats were placed in one of three groups: 1) normal dietary calcium with normal cholecalciferol; 2) low dietary calcium with normal cholecalciferol; or 3) normal dietary calcium with cholecalciferol supplementation. Blood 210Pb levels were determined at 3, 6, 12 and 24 hours following the administration of either an oral or an IP dose of 210Pb. Femur and kidney 210Pb activities were subsequently determined for all animals 24 hours after the administration of 210Pb. Cholecalciferol supplementation resulted in increased net intestinal absorption of 210Pb with uptake into femurs and kidneys. The effect of cholecalciferol to increase tissue uptake of 210Pb was shown to be independent of the effect of cholecalciferol on the gastrointestinal absorption of lead. A lowering of dietary calcium was shown to increase lead absorption with uptake into femurs; however, this increased tissue uptake of lead was shown to be dependent upon increased intestinal lead absorption and was not a direct effect of the low calcium diet.     

The effect of chelating agents on lead excretion in rats in relation to age.

The purpose of the present work was to determine the influence of age on the effectiveness of chelating agents in enhancing lead elimination from the body.Using the method of ²⁰³Pb-labeling, three doses of lead in the form of acetate (1.0 μg/kg, 0.5 mg/kg, 5.0 mg/kg) were applied intraperitoneally or intravenously to female albino rats aged 15 days and 18 weeks. Solutions of EDTA and of BAL (0.2 mmole/kg) were administered by a single or repeated intraperitoneal injection immediately after lead had been given. The whole body retention of ²⁰³Pb was measured at various time intervals in a twin crystal assembly.Both chelating agents caused a lower excretion of lead in 15-day-old rats than in adult animals. The poorer efficiency of chelating compounds in immature organisms was found to be independent of the lead dose, route of lead administration, chelating agent:metal molar ratio, and frequency of chelating treatment. The authors introduce the concept of a lower “free lead” level, due to a higher stability and/or inertness of lead linkages with body ligands in the growing organism as an explanation of the results obtained.     

牛磺酸对铅中毒大鼠红细胞免疫功能损伤的治疗作用

目的　了解牛磺酸对铅中毒大鼠红细胞免疫功能的影响。方法　把30只Wistar大鼠随机分为正常对照组、铅染毒对照组、治疗组,每组10只动物。对照组用蒸馏水灌胃,其余组用6 g/L醋酸铅溶液按每次60 mg/kg灌胃;染毒30 d后,治疗组动物用400 mg/kg的牛磺酸每天灌胃1次,正常对照组及铅染毒对照组用等剂量蒸馏水灌胃,连续30 d。采用酵母菌花环试验测定红细胞C3b受体花环率(RBC- C3b -RR)和红细胞免疫复合物花环率(RBC- CIC -RR)。结果　染毒对照组RBC C3b RR明显低于正常对照组(P<0 .01),其RBC- CIC- RR明显高于正常对照组(P<0 .01),治疗组的RBC- C3b- RR明显高于染毒组(P<0. 01),而其RBC CIC RR明显低于染毒组(P<0. 05)。结论　牛磺酸对铅中毒大鼠红细胞免疫功能的损伤具有明显的保护作用。     

Enrichment of (n-3) fatty acids of suckling rats by maternal dietary menhaden oil

The study was undertaken to determine whether the content of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in neonatal rats can be increased through milk provided by lactating mothers fed a diet containing 20% menhaden oil (experimental group), in comparison with a group fed a 20% corn oil diet (control group). The test diets were isocaloric and provided 41% of total energy as fat. Coinciding with 3-9% higher maternal body weight gain throughout the lactation period with the menhaden oil diet, the suckling rats in the experimental group at the ages of 3-9 d gained 5-10% more weight than did their control counterparts. When compared with corn oil, maternal dietary menhaden oil induced not only a higher weight percentage but also higher concentrations (microgram/mL) of EPA, DHA and total (n-3) fatty acids in milk, plasma, platelets and erythrocytes of neonates. These changes were accompanied by lower arachidonic and linoleic acid levels. EPA and DHA were detected in all three blood components of the control group, whose corn oil diet contained linolenic acid but not longer chain (n-3) fatty acids. This finding, together with the higher DHA to EPA ratios found in the three blood components than in the milk of the experimental group, suggests that neonatal rats possess the enzymes necessary for producing DHA from EPA and linolenate by desaturation and elongation mechanisms.