Absorption, transport and tissue storage of essential trace elements

Abstract

Intestinal absorption of many essential trace elements probably occurs by saturable and carrier-mediated processes. The nature and efficiency of these are influenced by a range of physiological, nutritional and genetic variables. Special emphasis is given to the influence of exogenous and endogenous ligands of small molecular mass in the intestinal lumen on absorptive efficiency. The effect of enterocyte proteins such as metallothionein which, by sequestering metals, influence their fate during absorption is also considered. Changes in the metabolic activity of the intestinal mucosa induced by copper or zinc deficiencies influence the fate of other nutrients, either by inhibiting intracellular transport or by preventing the degradation of potential antagonists of absorption. Conflicting evidence of roles for plasma albumin, transferrin and caeruloplasmin in the transport of zinc and copper is considered. The extent, location and form in which trace elements are stored in tissues differs between elements and between species. Retention and utilization are also influenced by pregnancy, lactation, stage of foetal development and by genetic variables. Better definition of the effects of these variables would improve the validity of estimates of the trace element requirements of man and other animals.

Trophic transfer of essential elements in the clownfish Amphiprion ocellaris in the context of ocean acidification

“…Among the affected processes, it is interesting to focus on the acid-base balance and the ionoregulation in the context of the trophic transfer of essential elements. Indeed, dietary trace element absorption occurs mainly in the intestine [30,31], and in marine fish (drinking water species), the intestine is also involved in acid-base balance and the ionoregulation (with gills and kidney [32,33]). Hereto, even if previous studies provided evidence of disturbances caused by p CO 2 on these processes in the fish intestine [34,35], our results indicated that it does not affect dietary essential element transfer in clownfish.…”

Prenatal Detection and Prevention of Neural Tube Defects in South Wales

“…Much of the folic acid in food may be destroyed in storage, in processing or in the prepartion of meals. Lack of dietary zinc may also interfere with folic acid absorption from the gut (Tanura, Shane et al, 1978) and on the analogy with absorption of zinc, folic acid absorption could be inhibited by excessive amounts of refined carbohydrates and fats in the diet (Benner and Mills, 1981;Elmes, 1983). Folic acid metabolism appears to be deranged in some women on oral contraceptives (Shojonia and Homaby, 1973) and a greater proportion of women who have just had a child with an NTD show evidence of folic acid metabolism than do women with a normal outcome (Hibbard and Smithells, 1965).…”

Intraluminal bioavailability of divalent cations

“…The fate of ions that readily form insoluble salts such as sulfides, phosphates, or hydroxides (including calcium, zinc, and magnesium) will be influenced by the changes in pH, microbial activity, and by the concentration and metal-binding affinity of endogenous ligands that are secreted into the lumen [2]. The fate of ions that readily form insoluble salts such as sulfides, phosphates, or hydroxides (including calcium, zinc, and magnesium) will be influenced by the changes in pH, microbial activity, and by the concentration and metal-binding affinity of endogenous ligands that are secreted into the lumen [2].…”

“…On the other hand, some organic ligands, such as amino acids derived from protein digestion, can form soluble complexes with cations and modify the inhibiting action of phytate or oxalate [2,7]. The best known examples of organic antagonists are phytate and oxalate.…”