Dietary fluoride prevents phosphorus-induced nephrocalcinosis in female rats

Dietary cholesterol lowers the activity of butyrylcholinesterase (EC 3.1.1.8), but elevates that of esterase-1 (EC 3.1.1.1) in plasma of rats

The question addressed is whether an increased intake of cholesterol affects esterase-1 (EC 3.1.1.1; ES-1) and butyrylcholinesterase (EC 3.1.1.8) activity in plasma. Rats were fed on a purified diet either without or with cholesterol (10 g/kg) added at the expense of the carbohydrate source. Dietary cholesterol significantly decreased plasma butyrylcholinesterase activity, but raised plasma ES-1 activity. Evidence is discussed, suggesting that plasma butyrylcholinesterase is involved in plasma cholesterol metabolism, whereas esterase-1 is involved in intestinal cholesterol absorption.

Thyroid function in rats with iodine deficiency is not further impaired by concurrent, marginal zinc deficiency

The hypothesis tested was that Zn deficiency aggravates impaired thyroid function as induced by I deficiency. In two separate experiments male rats were fed on diets either deficient in Zn or in I, or deficient in both. An identical, restricted amount of food was given to each rat so that body-weight gain of the experimental groups was comparable. Zn deficiency was evidenced by reduced tibial Zn concentrations. I deficiency was evidenced by goitre, reduced urinary I excretion, reduced plasma thyroxine concentrations and reduced absolute amounts and concentrations of thyroxine in the thyroid. Zn deficiency had no effect on the raised thyroid weight as induced by I deficiency. Zn restriction from 184 mumol Zn/kg diet to 31 mumol Zn/kg diet, but not to 92 mumol Zn/kg diet, significantly lowered plasma thyroxine concentration. There were no interrelated effects of Zn and I deficiencies on thyroid hormone levels. These results indicate that marginal Zn deficiency does not influence thyroid hormone metabolism in I deficiency.

Lowering effect of dietary milk-whey protein v. casein on plasma and liver cholesterol concentrations in rats

The effect of dietary whey protein v. casein on plasma and liver cholesterol concentrations was investigated in female, weanling rats. Balanced, purified diets containing either whey protein or casein, or the amino acid mixtures simulating these proteins, were used. The high-cholesterol diets (10 g cholesterol/kg feed) had either 150 or 300 g protein or amino acids/kg feed. The diets were fed for 3 weeks. At the low dietary protein level, whey protein v. casein did not affect plasma total cholesterol, but lowered the concentration of liver cholesterol. At the high dietary protein level, whey protein significantly lowered plasma and liver cholesterol and also plasma triacylglycerols. The hypocholesterolaemic effect of whey protein was associated with a decrease in very-low-density-lipoprotein cholesterol. At the high dietary protein concentration, whey protein reduced the faecal excretion of bile acids when compared with casein. The effects of intact whey protein v. casein were not reproduced by the amino acid mixtures simulating these proteins. It is suggested tentatively that the cholesterol-lowering effect of whey protein in rats is caused by inhibition of hepatic cholesterol synthesis.

Impaired iron status in rats as induced by copper deficiency

The hypothesis was tested that marginal copper deficiency affects iron status. Copper restriction (1 vs 5 mg Cu/kg diet) significantly lowered iron concentrations and transferrin saturation in plasma and reduced blood hemoglobin, hematocrit, and iron concentrations in tibia and femur, but raised iron concentrations in liver. Marginal copper deficiency did not affect feed intake and bodyweight gain.

Dietary fructose vs glucose does not influence iron status in rats

The effect of dietary fructose vs glucose on iron status was studied in rats. Female rats were fed for 4 wk diets containing either fructose or glucose (709.4 g monosaccharide/kg). Fructose vs glucose lowered iron concentrations in liver, kidney, and heart, but did not alter absolute iron contents.

Dietary iron loading does not influence biliary iron excretion in rats

The effect of dietary iron loading on biliary iron excretion was investigated with male Wistar rats aged 6 wk. The rats were fed purified diets with either 174 or 1740 mg FeSO4. 7H2O/kg diet and demineralized water for 6 wk. Blood haemoglobin, hematocrit, and iron concentrations in kidney and heart were not affected and iron concentrations in liver, spleen, and tibia were significantly raised after feeding the high-iron diet. The high-iron diet did not raise biliary iron excretion, suggesting that biliary iron excretion does not play an important role in regulating iron metabolism in rat after dietary iron loading.

Iron status in rats fed a purified diet without vitamin A

The effect of vitamin A deficiency on iron status was investigated in rats. After 28 d of feeding either low or high vitamin A diets (0 vs 4000 IU of vitamin A per kg feed), the final body weight was slightly but significantly lowered by the low vitamin A diet. Plasma retinol concentrations were decreased in rats fed diets low in vitamin A. Marginal vitamin A deficiency produced slightly, but significantly lower blood hemoglobin concentrations; it did not clearly affect hematocrit. The concentration of iron in liver was significantly higher when diets low in vitamin A were fed while significantly lower levels were observed in femur.

High intakes of tin lower iron status in rats

The effects of relatively low (1, 10, and 50 mg/kg) and high (100 and 200 mg/kg) dietary concentrations of tin (added as stannous chloride) on iron status of rats were determined. After feeding the diets for 28 d, feed intake and body weights were not significantly affected. Iron concentrations in plasma, spleen, and tibia as well as percentage transferrin saturation were decreased in rats fed the diets supplemented with 100 or 200 mg tin/kg. In rats fed the diet containing 200 mg tin/kg, group mean hemoglobin, hematocrit, and red blood cell count were slightly lowered but total iron binding capacity was not affected. Iron status was not influenced by dietary tin concentrations lower than 100 mg/kg. If these results can be extrapolated to humans, then it may be concluded that tin concentrations in the human diet, which range from 2 to 76 mg/kg dry diet, do not influence iron status in humans.

Liver and plasma copper concentrations in rats fed diets containing various proteins

The question was addressed whether the type of dietary protein influences copper (Cu) concentrations in liver and plasma of rats. For this purpose, weanling female rats were fed diets containing as the sole source of protein either soybean protein, casein, amino acid mixtures simulating soybean protein or casein, lactalbumin, ovalbumin, or herring meal. The diets were balanced for residual Cu in the protein preparations. The type of protein and the composition of the amino acid mixture did not differentially influence liver Cu concentrations. Liver Cu was significantly lowered after feeding the amino acid mixtures when compared with the intact proteins. Plasma Cu concentrations were not affected by the type of protein in the diet.