I. Rabar

Age and intestinal retention of mercury and cadmium in rats

The site of cadmium and mercury retention in the intestine was determined in 6-day-old sucklings and 6-week-old weaned rats 6 days after oral administration of 115mCd and 203Hg. The ileum was found to be the main site of intestinal retention of both cations in sucklings but not in weaned rats. Other age- and element-specific differences in the site of metal retention in the intestine were also found. These differences indicate that even in neonates, metal absorption might be a more specific process than previously assumed.

Simultaneous reduction of radioactive strontium, caesium and iodine retention by single treatment in rats

The effect of a mixture of calcium alginate, iron (III) ferrocyanide and potassium iodide added to rat diet on 85Sr, 137Cs and 131I metabolism and health was investigated in female rats after four weeks of treatment. The retention of these radioisotopes was determined in the whole body and critical organs six days after 85 Sr and 137CS and one day after 131I oral administration. The health effect of the mixture was evaluated by measuring body weights, haematological parameters, concentrations of iron, zinc and manganese in the kidneys, liver and femur, bone parameters (femur composition and morphometry) and by a histopathological examination. The mixture reduced 85Sr retention in the femur 11 times, 137Cs retention in the thigh muscle 102 times and 131I retention in the thyroid 134 times. Treated animals were in good health and the only differences found between the control and experimental rats were slightly lower haemoglobin values in the blood and a slightly lower iron concentration in the liver. It is concluded that the mixture was very efficient for decreasing body retention of three important fission products and that it can be used over long periods without causing adverse health effects.

The effect of iron additive to milk on cadmium, mercury, and managanese absorption in rats

Abstract Six-day-old sucklings and 6-week-old female rats were used in the experiment to estimate whether low iron content of milk is the reason for increased gastrointestinal absorption of metals. The absorption of 115mCd, 203Hg, and 54Mn was determined by measuring the body retention (whole body, carcass, and gut) 6 days after oral administration. To sucklings radioisotopes were administered by artificial feeding with cows milk with or without 100 ppm Fe additive. Iron addition had no influence on metal absorption at this age. The same radioisotopes were administered by stomach tube to older animals fed rats diet or milk with or without 100 ppm Fe additive. Increased iron content of milk decreased the absorption of all metals. For mercury and cadmium most of this effect was due to decreased gut retention and only partly to decreased carcass retention. It is concluded that the high absorption of metals in sucklings is not likely to be due to the low iron content of milk and also that iron does not interact with cadmium, mercury, and manganese in the absorption process at this age.

Bioavailability of cadmium in rats fed various diets

Six-week-old female albino rats were fed rat diet or human foods: meat, bread or milk — 3 days before and 6 days after a single oral dose of 115mCd. All animals were killed 6 days after administration and the radioactivity in the whole body and in the gut-free carcass was determined in a double scintillation counter. Gut retentions were calculated as the difference: whole body minus carcass. All animals fed meat, bread or milk had much higher body retentions than animals fed rat diet (whole body 4–5 times, carcass about 3 times and gut 10–14 times). Our results point out the importance of nutritional factors in metal metabolism and toxicity.

Effect of rat's diet on 85Sr, 115mCd, and 203Hg absorption in suckling rats

Abstract Six-day-old suckling rats were artificially fed over 8 hr with cows milk or rats diet labeled with 85 Sr, 115 m Cd, or 203 Hg. The whole-body radioactivity was determined in a double-crystal scintillation counter every 24 hr over a 6-day period. Rats diet caused a reduction in the whole-body retention of all radioisotopes which was highest for 203 Hg and lowest for 85 Sr. All sucklings were killed 6 days after the radioisotope administration and the radioactivity was determined in the carcass and in the gut. Rats diet reduced carcass retention by about 10% for 85 Sr, and two and three times for 115 m Cd and 203 Hg, respectively. Rats diet also reduced gut retention by about 20% for 85 Sr, two times for 115 m Cd and eight times for 203 Hg. It is concluded that dietary factors are partly responsible for the high metal absorption in sucklings. This specially applies to mercury because rats diet caused a considerable reduction in the whole-body retention of this metal primarily by decreasing its gut retention.

Effect of a Metal Mixture in Diet On the Toxicokinetics and Toxicity of Cadmium, Mercury and Manganese in Rats

The purpose of this work was to determine whether a metal mix ture added to diet influences the toxicokinetics and toxicity of some elements. The metal mixture (MM) used in these experiments was ash (slag) from a coal gasification plant. The effect of this mixture (5 percent in diet) on the toxicokinetic and on the acute or subchronic toxicity of Cd, Hg, Mn was determined in rats of different ages. Rats were exposed for five weeks in toxicokinetic and six weeks in acute tox icity experiments. Sucklings were exposed through their mothers, which received the MM in diet over the pregnancy and lactation period. In toxicokinetic studies, half of the animals additionally received Cd, Hg or Mn (100, 50 or 2000 ppm, respectively) in drinking water. In subchronic experiments, six-week-old albino rats of both sexes were given MM in the diet and Cd, Hg or Mn in drinking water for 16 weeks. In toxicokinetic studies, 115mCd, 203 Hg or 54Mn were administered orally or intraperitoneally to mothers and pups. Exposure to MM had no effect on the absorption, retention and organ distribution of these elements determined six days after radioisotope administra tion. In acute toxicity studies, exposure to MM in diet had no effect on LD 50 values obtained eight days after oral administration of Cd, Hg or Mn to rats of different ages. In subchronic experi ments, the effect of individual metals (Cd, Hg or Mn) was similar in animals with and without simultaneous exposure to the metal mixture (only a slight potentiation of a few health-effect parameters of cadmium was noticed in some animals). It is concluded that oral exposure to MM in the diet had almost no effect on the toxicokinetics and toxicity of Cd, Hg and Mn. This could be explained by the low level or low bioavailability of ele ments from MM, by the metal-metal interaction within the mixture or by the choice of health effect indicators determined. These results are presented as one of the potential approaches for study ing the health effect of a metal mixture as occurring in the environment.

Effect of milk on mercury absorption and gut retention in rats

The retention of 203Hg was studied six days after a single oral or intraperitoneal administration to six week old female albino rats fed rats diet or milk. After oral administration rats on milk diet had a two times higher retention of mercury in the gut-free carcass and a 23 times higher retention in the gut than animals on rats diet. Changes in diet had very little influence on mercury retention after intraperitoneal administration. The higher gut and carcass rentions of mercury in animals on milk diet could be prevented or reduced by transferring rats from milk diet to rats diet several days after an oral dose of mercury. These results might be relevant for interpreting high gut and carcass retention after oral administration of some metals in suckling and changes which occur at weaning.

More data on mercury absorption in relation to dietary treatment in rats

The kinetics of mercury (Hg) absorption in relation to diet by determining whole body (WB), carcass (C) and gut (G) retention in control and milk-fed rats 6, 9, 12 and 15 days after oral administration of 203Hg have been studied. All retention values were higher in the milk-fed than in control rats during the experimental period. The higher WB retention in the milk-fed animals was primarily due to increased G retention especially at shorter time intervals. Animals on the milk diet had in the C, higher retention values, and in the G, higher retention and longer residence time. There was no evidence that Hg from the gut compartment entered into other parts of the body within the observation period. More evidence is needed about the effect of other dietary treatments on Hg metabolism.

Chronic and reproduction studies in rats exposed to gasifier ash leachates

Ash from the coal gasification process contains a broad spectrum of elements which through leaching (gasifier ash leachates) may enter into the environment. The health effect of such leachates i.e. complex mixtures of inorganic elements is insufficiently known. We investigated the effect of gasifier ash leachates in a chronic-(9-month) and in a three-generation reproduction study. The leachates were prepared weekly by water extraction of ash from a Lurgi coal gasification plant in Yugoslavia, and given to experimental animals instead of drinking water. In the chronic experiment exposed animals showed no changes in mortality rate, haematological findings, concentration of Fe, Zn, Mn in kidneys, liver, testicles and femur, as well as in femur composition and morphometry, gross pathology and organ histology. In the reproduction study the number of pregnancies, weight and number of newborns, and concentration of Fe, Zn, Mn in carcasses of sucklings were the same in control and experimental animals.

Failure of Trace Element Additives to Decrease Cadmium, Mercury, and Manganese Absorption in Suckling Rats

Age is recognized to play an important role in metal metabolism and toxicity (Nordberg et al. 1978). The high gastrointestinal absorption of metals in the neonatal age was partly attributed to the only nutrient, i.e., milk which was shown to increase the metal absorption also in older animals (Kostial et al. 1978). Milk has a low content of trace elements (Underwood 1977) so it was supposed that this could be one possible explanation for the high absorption in neonates.