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Biomedical subjects

A Nahapetian

Publications and source records attributed to A Nahapetian.

9 recordsLinked to original sources
PubMed1982

Selenium metabolism in healthy adults: quantitative aspects using the stable isotope 74SeO3(2-).

Using the novel method of stable isotopes, kinetics of appearance and disappearance of 74Se in feces, blood, and urine from four young adult males given single and multiple oral doses of 74SeO32- are described. It is shown that this method is suitable as an alternative to the use or radioselenium and permits detailed evaluation of both kinetics and quantitative aspects of absorption, excretion, and retention of selenium in human subjects. The data provided in this manuscript generally confirm the current understanding of the role of gastrointestinal tract and the kidneys in regard to the regulation of selenium nutriture of human subjects. From the peak appearance of the ingested label in urine it is apparent that there is an early preferential urinary excretion of he ingested label in comparison with the native plasma selenium. The present methodology is readily applicable in detailed studies of urinary forms of the excreted label and elucidation of the time course of metabolism of the ingested label as regards its conversion to the urinary metabolites.

Absorption↗
PubMed1982

Selenium bioavailability with reference to human nutrition.

Various aspects of selenium metabolism and nutrition in relation to the question of selenium bioavailability in foods and the diet of man are reviewed. Few published studies exist on selenium metabolism in human subjects, particularly those representative of healthy individuals in the United States. Animal studies reveal that various factors, including the source and chemical form of selenium in foods and feeds, influence selenium bioavailability. However, the quantitative significance of animal assay data for human nutrition is not known. The limited number of published studies in man suggest that the metabolic fate and physiological function of dietary selenite may differ from that of selenomethionine or of food selenium. However, much additional research will be required to establish an adequate picture of the significance of dietary selenium bioavailability in human nutrition and health. Based on initial human experiments carried out at the Massachusetts Institute of Technology, use of stable isotopes of selenium offers promising opportunities for closing the gap of knowledge that now exists concerning the role and significance of factors that determine how the selenium present in foods is used to meet the physiological requirements of the consumer.

Absorption↗
PubMed1980

Metabolism of 14C-phytate in rats: effect of low and high dietary calcium intakes.

The purpose of this study was to explore in rats the in vivo metabolism of phytate, using [U-14C]phytate and to assess the effects of calcium intake on phytate and myo-inositol metabolism. Labeled phytate was prepared from wheat following injection of the plants at the milk stage with [U-14C]myo-inositol. Groups of 30-day-old male rats were adapted for at least 6 weeks either to a low-calcium (2.9 mM/100 g dry diet) or a high-calcium (30.6 mM/100 g dry diet) cereal-based diet. They were then transferred to metabolic cages, continued on their respective diets and given an oral dose of [14C]phytate or [14C]myo-inositol. Appearance of radioactivity in expired air, feces and urine was monitored for 48 hours; the rats were then killed for determination of 14C-activity in liver, kidneys, blood and femur. The high-calcium diet significantly increased the output of radioactivity in feces (54% of dose) and reduced the appearance of radioactivity in expired air (25% dose) and in body tissues following 14C-phytate administration. The high-calcium intake did not affect the fate of [14C]myo-inositol (96% of dose). These results suggest that phytate or a derivative(s) is almost quantitatively absorbed (94% of dose) when calcium intake is low (Ca/P molar ratio; 0.21) and it is extensively oxidized to CO2 (60% of dose). Thus, a high-calcium intake (Ca/P molar ratio; 2.24) inhibits the utilization of [14C]phytate. Hence, it is suggested that the impact of dietary phytate on trace mineral bioavailability will depend upon the presence of factors, including excess calcium, that alter the absorption and utilization of phytate.

Animals↗