Alpha- and gamma-tocotrienols are metabolized to carboxyethyl-hydroxychroman derivatives and excreted in human urine.

Limited information is available regarding metabolism of vitamin E forms, especially the tocotrienols. Carboxyethyl-hydroxychromans (alpha- and gamma-CEHC) are human urinary metabolites of alpha- and gamma-tocopherols, respectively. To evaluate whether tocotrienols are also metabolized and excreted as urinary CEHC, urine was monitored following tocotrienol supplementation. Complete (24 h) urine collections were obtained for 2 d prior to (baseline), the day of, and 2 d after human subjects (n = 6) ingested tocotrienol supplements. The subjects consumed 125 mg gamma-tocotrienyl acetate the first week, then the next week 500 mg; then 125 mg alpha-tocotrienyl acetate was administered the third week, followed by 500 mg the fourth week. Urinary alpha- and gamma-CEHC were measured by high-performance liquid chromatography with electrochemical detection. Urinary gamma-CEHC levels rose about four- to sixfold in response to the two doses of gamma-tocotrienol and then returned to baseline the following day. Significant (P < 0.0001) increases in urinary alpha-CEHC were observed only following ingestion of 500 mg alpha-tocotrienyl acetate. Typically, 1-2% of alpha-tocotrienyl acetates or 4-6% of gamma-tocotrienyl acetates were recovered as their respective urinary CEHC metabolites. A gamma-CEHC excretion time course showed an increase in urinary gamma-CEHC at 6 h and a peak at 9 h following ingestion of 125 mg gamma-tocotrienyl acetate. In summary, tocotrienols, like tocopherols, are metabolized to CEHC; however, the quantities excreted in human urine are small in relation to dose size.

Effect of dietary fluoride on selenite toxicity in the rat.

Three factorial experiments were conducted to determine if high dietary fluoride (F) would inhibit selenite toxicity in rats. Initially, three levels of selenite (0.05, 3, and 5 mg/kg diet) were matched against three levels of F (2, 75, and 150 mg/kg diet). Fluoride failed to prevent the depressive effect of selenite on 8-wk food intake and body wt gain. Selenium (Se) concentration of plasma and kidney and enzymatic activity of whole blood glutathione peroxidase (GSH-Px) were also unaffected by F. Liver Se concentration, however, was slightly (12%) but significantly (p < 0.025) reduced when the highest F and Se levels were combined. Fluoride (150 mg/kg) appeared to reduce liver selenite toxicity (5 mg/kg). Therefore, further study focused on liver histology with treatments that eliminated the middle levels of selenite and F. Fluoride prevented the hepatic necrosis seen in selenite-toxic rats. Similar histological lesions were not observed for kidney or heart. Fluoride partially (26%) but significantly (p < 0.025) reduced thiobarbituric-reactive substances in selenite-toxic rats, but there was no F effect on intracellular distribution of liver Se, glutathione levels in liver and kidney, or on liver xanthine oxidase activity. Overall, the protective effect of F on selenite toxicity appears to be confined to liver pathology. The exact mechanism for this effect, however, remains unclear.

Chloride determination in foods with ion-selective electrode after isolation as hydrogen chloride.

This report describes a sample preparation method in which chloride is isolated as hydrogen chloride from food samples prior to analysis with the chloride ion-selective electrode. Chloride analyses of selected foods with this method agreed with chloride values reported in food composition tables. Chloride analysis with the present procedure also agreed with the certified value for the chloride content of the National Bureau of Standards (NBS) Standard Reference Material, Nonfat Milk Powder. Reliability of the chloride isolation procedure was evident by the complete recovery of chloride added to food samples and a narrow range of 95% confidence limits calculated for each set of analyses. The usefulness of the chloride ion-selective electrode to determine chloride in foods is greatly enhanced by this procedure because matrix interference by other sample components is removed prior to analysis.

Influence of dietary lead on fluoride bioavailability in the rat.

A factorial experiment was conducted with weanling rats fed a purified diet to determine the influence of dietary lead (0 or 100 ppm) as either lead acetate or lead carbonate on fluoride bioavailability (2 or 10 ppm as sodium fluoride). During the 6-wk study, both forms of lead depressed weight gain, regardless of the fluoride level, despite the fact that food intake was similar for all treatment groups. Both forms of lead produced a small, but significant, reduction in femur and second molar fluoride. This effect, however, could only be demonstrated in rats fed diets containing 10 ppm fluoride, indicating a significant interaction between lead and fluoride for these indices of fluoride bioavailability. This interactive effect between fluoride and lead was also demonstrated for apparent fluoride absorption. Both forms of dietary lead significantly increased the lead concentration of plasma, femur, liver, and kidney, and both forms of lead significantly increased the urinary excretion of delta-aminolevulinic acid. The level of dietary fluoride failed to influence these measurements. We therefore conclude that, although small amounts of dietary lead reduce fluoride bioavailability, small amounts of dietary fluoride do not appear to significantly influence the utilization of dietary lead.

Influence of dietary chloride on fluoride bioavailability in the rat.

A factorial experiment was conducted with weanling rats fed a purified diet to determine the influence of dietary chloride (0.02, 0.10 and 0.50%) as sodium chloride on fluoride bioavailability (2 or 10 ppm as sodium fluoride). After 6 wk, rats fed the lowest chloride-containing diets had significant reductions of plasma chloride, urinary chloride excretion and growth rate compared to other chloride groups. Depressed growth occurred in rats fed chloride-deficient diets despite the fact that food intake was similar for all treatments. Fluoride retention was greatest in chloride-deficient rats, which was reflected in enhanced skeletal uptake of fluoride. Fluoride absorption was not inhibited by high chloride intake. We therefore conclude that emphasis on the effect of chloride on fluoride bioavailability should be directed towards an enhancement of fluoride retention by low salt (sodium chloride) diets rather than in terms of a possible negative effect of a high salt diet on fluoride absorption.

Influence of zinc and iron on dietary fluoride utilization in the rat.

Two experiments were conducted with the weanling rat fed a purified diet to determine the influence of dietary zinc (6, 30, 150 ppm) and iron (7, 35, 175 ppm) on fluoride bioavailability. Dietary fluoride in each case was 2 or 10 ppm as sodium fluoride. During a 6-wk trial, neither divalent zinc nor divalent iron affected fluoride bioavailability based on skeletal uptake of fluoride. Our studies were specifically designed to provide concepts about the effects of dietary trace element supplementation practices on dietary fluoride bioavailability especially in terms of fluoride originating from foods prepared in fluoridated water. Our results suggest that either iron or zinc can be added to foods to improve nutritional value without compromising the availability of food fluoride.

Uptake of(75)Se in cataractous rat lens proteins.

The purpose of the present study was to measure the pattern of uptake of(75)Se into proteins in normal rat lenses and into the proteins of lenses with selenite-induced cataract. Ten-day-old suckling rats received a single injection of(75)Se with or without a cataractous dose of cold carrier sodium selenite. Four days after injection, the proteins from excised lenses were counted for(75)Se radioactivity and subjected to gel permeation chromatography, amino acid analyses, and mass spectrometry. All three soluble crystallin lens proteins took up(75)Se in both normal and cataractous lenses. However, cataractous lenses did not take up(75)Se into a soluble protein in which major quantities of(75)Se were taken up in normal rats. Futhermore,(75)Se in the gamma-crystallins was associated with an unusual acidic amino acid. It was concluded that selenium metabolism by lens proteins may be unusual compared to other soft tissues.

Inducibility and amounts of metallothionein as influenced by cadmium and zinc in the developing rat.

Information on the accumulation and/or depletion of Zn in metallothionein (MT) of rat fetus, rat pup, and maternal rat liver at various ages was obtained with pregnant rats fed a basal casein diet or this diet plus either 100 ppm Zn or 50 ppm Cd. Rats fed each of the respective diets were sacrificed on 12, 16, and 20 d of gestation and 0, 7, 14, and 28 d post-partum. No Cd was detected in the placenta or fetal tissue and the Cd did not affect the accumulation of Zn in the fetal MT, but it did increase the Zn content in liver MT of the dams. Very little Zn in MT was found on day 12 of gestation, but Zn rapidly increased in MT to a maximum at time of birth. The accumulation of Zn in MT was independent of the diet for the fetuses, but the Zn accumulation in the dam and pup tissues was diet dependent. In order to study age-dependent difference in the inducibility of MT, newborn, 5-week-old, or 24-week-old rats were injected with zinc at the levels of 0, 3, 6, or 9 mg/kg and 5 h later injected with(35)S-cystine. In rats sacrificed 1 h later, the amount of radioactivity in liver MT demonstrated that this protein in older animals was more readily induced by Zn than in younger animals.

Petroleum refinery wastewater induction of the hepatic mixed-function oxidase system in Pacific staghorn sculpin.

Induction of hepatic microsomal cytochrome P450 and aldrin epoxidase was observed in the estuarine sculpin (Leptocottus armatus), following in vivo exposure to Class B petroleum refinery effluent from two West Coast refineries. The data demonstrate the presence and inducibility of the mixed-function oxidase system in Leptocottus armatus. Differences in the extent of mixed-function oxidase induction between the two effluents may be related to differences in wastewater chemistry.

Effects of petroleum refinery wastewater exposure on gill ATPase and selected blood parameters in the Pacific staghorn sculpin (leptocottus armatus).

1. The effects of in vivo exposure to various concentrations of petroleum refinery wastewater on gill ATPase, plasma protein, plasma osmolarity, and hematocrit were measured in the euryhaline fish, Leptocottus armatus. 2. The extent of the reduction in Na,K-ATPase activity resulting from the exposure to the two refineries wastewaters may be related to wastewater chemical composition. 3. Changes in the blood chemistry parameters did not follow a consistent or easily explainable pattern.

Long-term turnover of cadmium metallothionein in liver and kidney following a single low dose of cadmium in rats.

Rats were injected subcutaneously on two consecutive days with CdCl2, and sampled animals, killed at monthly intervals from 1 to 6 months thereafter, exhibited the presence of Cd,Zn-thionein in both the liver and kidney. At 6 months, hepatic thionein was present as the two major polymorphic forms previously demonstrated in short term Cd-injection studies. [35S]cysteine incorporation studies showed that both polymorphic forms of thionein underwent continual turnover at similar rates throughout th study. The slow hepatic and renal turnover of Cd, therefore, was not due to a highly stable form of Cd-thionein, but apparently due to an inefficient mechanism for excretion of Cd from these tissues. The Cd/Zn ratio of hepatic thionein remained relatively constant, suggesting that continual thionein induction results in a long-term hepatic trapping of Zn by thionein, but the ratio of renal thionein showed a marked increase during the course of the study.

Interactions of zinc and selenium on the binding of cadmium to rat tissue proteins.

The administration of cadmium to rats by either oral or injection routes causes zinc to accumulate in the low molecular weight (MW) protein metallothionein (MT) of liver and kidney, but not in a low MW protein in the testis. Preliminary evidence indicates that the low MW cadmium-binding protein in testes is not MT. Feeding high levels of zinc to rats results in its accumulation with tissue MT, and the zinc is very labile. In contrast, the zinc that accumulates in MT as the result of cadmium exposure is not very labile. In the reverse situation, zinc does not cause cadmium to accumulate in MT. The turnover of MT is shorter when saturated with zinc than when cadmium is the predominant metal bound to it. Even though selenium will counteract testicular damage due to cadmium, it causes cadmium to accumulate in this organ at higher levels than in animals exposed to cadmium without selenium. Injection of selenate, and selenide--but not selenomethionine or selenocystine--diverts the binding of injected cadmium from low MW proteins to high MW ones in the testes. Selenium injections had only minor influences on the binding of zinc to testicular proteins. In contrast, very little diversion occurred in the binding of either cadmium or zinc in tissues of rats fed high levels of selenium. The data suggest that it is the selenide form of selenium that causes the diversion of cadmium binding in tissues, thus providing protection of testes against cadmium exposure.

Isolation and partial characterization of a cadmium-binding protein from the American oyster (Crassostrea virginica).

American oysters (Crassostrea virginica) were exposed to 0.1 ppm cadmium for 0--15 days in a flowing seawater system and then placed into clean flowing seawater for 24 h prior to sacrifice. Whole oysters were homogenized and a cadmium-binding protein isolated and purified by a process of centrifugation, heat-treatment, Sephadex G-75 chromatography, DEAE cellulose chromatography and disc gel electrophoresis. A highly anionic protein which is not present in control oysters was found to be present in cadmium-exposed animals after 3 days of treatment and to increase in concentration at succeeding time points. The protein does not extensively bind zinc or copper. Amino acid analysis of the purified protein disclosed an amino acid composition characterized by a high percentage of dicarboxylic amino acids and relatively little cysteine.

Early cellular effects of circulating cadmium-thionein on kidney proximal tubules.

Circulating cadmium-thionein (Cd-MT) is cleared from the mammalian circulatory system by filtration through the kidney glomerulus with subsequent reabsorption by kidney proximal tubules. Damage to the tubules results following uptake of Cd-MT, which is dependent upon time and the dose level of cadmium administered. Intravenous administration of 109Cd-MT at doses of 0.017 and 0.17 mg Cd/kg body weight with examination of total renal uptake of 109Cd at 0.5, 3, and 24 hr disclosed that the rate of clearance from the blood and uptake by the kidney was significantly more rapid at the 0.017 mg Cd/kg dose. Ultrastructural changes resulting from intravenous injection of either form A or B of Cd-MT were characterized by increased numbers of pinocytotic vesicles and small, dense lysosomal structures. There was no evidence of mitochondrial swelling or cell death at either 3 or 6 hr after injection. The subcellular distribution of cadmium in kidney tissue at various times after administration of Cd-MT was determined by using differential centrifugation techniques with 109Cd and in situ by using x-ray microanalysis. At 30 min after injection of Cd-MT, significant amounts of cadmium were present in lysosomal fractions indicating an interaction between the tubular lysosome system and Cd-MT prior to the onset of overt cellular toxicity. Results suggest that Cd-MT is reabsorbed and broken down by kidney tubule cells in a physiological manner with possible subsequent release of the toxic cadmium ion.

Fluoride-selenium interaction in the hard and soft tissues of the rat.

The interaction of dietary fluoride and selenium in the hard and soft tissues of rats was studied by providing drinking solutions containing 50 ppm F, as NaF, alone or plus 1 or 3 ppm Se as one of the following selenium compounds: NaSeO3, Na2SeO4, DL-selenomethionine, or DL-selenocystine. The following parameters were measured: symptoms of selenium toxicity, soft tissue uptake of fluoride and selenium, histology of liver and kidney tissues, fluoride uptake into growing femur bones, and fluoride uptake onto calcified molar enamel. No evidence was found that fluoride interacted with any of the four selenium compounds.