Oscar E. Olson

Investigations on selenium in wheat.

Abstract Pronase hydrolysates of crude gluten preparations from naturally seleniferous wheat seeds were subjected to ion-exchange chromatography and the eluates were examined chemically for selenium. Almost half of the selenium in the hydrolysate was accounted for as selenomethionine, but selenocystine was not detected. More detailed studies were then made on wheat gluten, seeds and straw from plants grown on soil to which 75Se-selenate had been added. On pronase hydrolysis of the seeds or the gluten, about half of the selenium could again be accounted for as selenomethionine. On examining protein-free, hot-water extracts of the seeds or straw of these plants, no free selenomethionine could be detected, suggesting the rapid incorporation of this amino acid into protein. Neither selenocystine, the seleno-half-cystine moiety nor Se-methylselenocysteine was detected in the hydrolysates or in the water extracts. The results suggest, however, the presence of selenocysteic acid in significant amounts in the gluten, the seeds and the straw. Over half of the selenium in the straw could be accounted for as selenate, but selenite was not found. Selenium compounds eluted shortly after selenite, selenate and cysteic acid, suggesting the presence of oxides of selenomethionine.

Identification of a major selenium excretory product in rat urine

Abstract 1. 1. Very few organic metabolites of selenium have been identified from mammalian systems. The objective of this study was to isolate selenium-containing metabolites from rat urine. 2. 2. A new selenium metabolite was isolated from the urine of rats injected with [ 75 Se]selenite. The metabolite was identified as a trimethylselenonium ion. Infrared spectra, nuclear magnetic resonance spectra, cocrystallizaton data and cochromatography data confirm the identity of the metabolite. 3. 3. Substantial amounts of trimethylselenonium ion (30–50% of urinary selenium per 24 h) are excreted after a single injected dose of selenite. It is a normal excretory product of selenite selenium.

Selenium Toxicity in Animals with Emphasis on Man

This review was undertaken to establish what might be the maximum safe dose of selenium that could be administered to man in studies on the use of the element in cancer prevention. The early history of selenium poisoning is briefly summarized. The literature on clinical signs and toxicity data for acute and for chronic selenosis in farm and experimental animals is discussed. Several cases of acute selenosis in man are reviewed, and a number of reports on chronic selenosis in man are reviewed and evaluated. Based on these, the maximum safe single oral dose of selenite, selenate, DL-selenocysteine, or DL-selenomethionine is suggested as 0.05 mg Se/kg body weight (milligrams of selenium per kilogram of body weight). The maximum safe multiple oral dose is suggested as 5 μg Se/kg body weight.

Trimethylselenonium ion as a general excretory product from selenium metabolism in the rat

Abstract 1. 1. Several sources of selenium were given to rats and the metabolites excreted in the urine were examined chromatographically. 2. 2. A recently identified product of selenite metabolism, (CH 3 ) 3 Se + , was shown to be a major excretory product from selenate, selenomethionine, selenocystine, Se- methylselenocysteine, and seleniferous wheat. The level of (CH 3 ) 3 ) 3 Se + in the urine was equivalent ot 20–50% of the urinary selenium depending on the selenium source and the collection time. 3. 3. A second major unidentified urinary metabolite was excreted from each radioactive selenium source and accounted for 11–28% of the total urinary selenium. 4. 4. On the basis of chromatographic evidence, the selenium-containing metabolites in rat urine seem to be familiar regardless of the original source of selenium.

Toxicity of trimethylselenonium chloride in the rat with and without arsenite

Abstract Trimethylselenonium chloride (TMSeCl) was submitted to a toxicologic evaluation in rats. The ip LD50 was 49.4 mg Se/kg. In the presence of 4 mg of As/kg injected as arsenite, the LD50 was reduced to 2–3 mg Se/kg. The toxicity of trimethylsulfonium iodide was similar to that for TMSeCl, but arsenite had no effect. To further examine the apparent synergism between arsenite and TMSeCl, the effect of arsenic on the elimination of TMSe-selenium in the breath and in the urine was studied. At different levels of selenium administration, 3–9% was exhaled, and this amount was increased by the injection of arsenite. On the other hand, arsenite injection reduced urinary selenium excretion. It was also found that arsenite and dimethyl selenide (DMSe) were more toxic in combination than when injected individually, but arsenite did not affect the exhalation of Se from DMSe. When TMSeCl was fed, levels above 240 ppm Se were required to reduce growth, and even at a level of 960 ppm Se, no deaths were observed in a 5-wk experimental period. The presence of arsenite in the diet slightly increased the toxicity of the TMSeCl administered in the diet at intermediate levels of selenium.

Selenoamino acids in tissues of rats administered inorganic selenium.

There are conflicting reports in the literature concerning the synthesis of selenoamino acids from inorganic selenium in animals, and this work was undertaken to further investigate this. Pronase digests of acetone powders of liver and kidney tissue from rats administered 75SeO3= were subjected to fractionation by cation exchange chromatography using current methods for separating the various amino acids. Very little, if any, selenocystine was found in the digests. However, good evidence was obtained for the occurrence of 2,7-diamino-4-thia-5-selenaoctanedioic acid. It is suggested that the selenocysteine portion of this compound was formed by the reduction of the selenite to selenide with its subsequent incorporation into the amino acid by the action of serine hydrolase (E C 4.2.1.22). No selenomethionine was found under the conditions of this study.

Distribution of Serum Selenium, Copper, and Zinc in Normal Human Pregnancy

The distribution of the serum levels of selenium, zinc, and copper in human pregnancy at various gestational ages were determined from two ethnically and geographically different populations (Rosebud Indian Reservation and southeastern South Dakota) of 410 normal subjects. As gestation age increased, there was a significant increase and a slight decrease in the mean levels of copper and zinc, respectively. No change in the levels of selenium was observed. Significantly higher levels of both pregnancy and non-pregnancy serum copper were observed in the Rosebud population compared to that in southeastern South Dakota, possibly due to the significantly higher level of copper in the Rosebud water. No differences were observed in the zinc or selenium levels between the two populations. Serial measurements of these trace metals during the third trimester of pregnancy were performed on 18 subjects, and supported the trends described for copper and selenium. No decrease in zinc was observed in the individual subjects.