Absorption Of Copper In Rats Research Articles

Short-term ingestion of chlorogenic or caffeic acids decreases zinc but not copper absorption in rats, utilization of stable isotopes and inductively-coupled plasma mass spectrometry technique.

The amount of dietary trace elements absorbed from a meal depends, among other factors, on the quantities of certain minor plant constituents present in the meal. These substances can act as ligands and bind trace elements in the digestive tract in available or unavailable forms for absorption. The present study was designed to investigate the extent to which different polyphenols (PP) may influence Zn and Cu absorption in rats. Different PP of nutritional interest (chlorogenic acid, caffeic acid, catechin and rutin) were studied using meals extrinsically-labelled with stable isotopes 67Zn and 65Cu. Male Wistar rats were fed on a non-labelled semi-synthetic diet containing (mg/kg) 38 Fe, 35 Zn and 7.5 Cu for 8 d. PP were dissolved in dimethyl sulfoxide as the solvent and added to the meal at 1 g/kg during 3 d before isotope administration and until the end of the experiment (a further 3 d). The control group received the dimethyl sulfoxide only. After overnight food deprivation, rats were fed on the labelled test meals (4 g diet +0.1 mg 67Zn and 0.1 mg 65Cu) with 0.5 mg Dy as a faecal marker. Faeces and urine pools were collected for 3 d and analysed for 67Zn and 65Cu isotopic enrichment using the inductively-coupled plasma mass spectrometry technique. Zn absorption was significantly less in rats fed on chlorogenic acid or caffeic acid than in the control group. Catechin ingestion non-significantly inhibited 67Zn absorption. However, the PP studied were without effect on Cu absorption. The study illustrates the effect of metal-binding phenolic compounds on mineral nutrition in the rat, and the possible importance of the effects of different foods rich in these compounds on mineral absorption in man.

Elevated Intestinal Absorption of Copper in Rats Fed on a Excessive Tyrosine Diet

Recently we reported increased serum levels of copper and of ceruloplasmin activity in rats fed a diet with excess tyrosine. In this study, we found increases in the apparent absorption of copper from the intestines and in the concentrations of kidney copper and metallothionein in rats on the same diet.

Inhibitory effect of high dietary zinc on copper absorption in rats. II. Binding of copper and zinc to cytosol proteins in the intestinal mucosa.

Earlier studies showed that high dietary zinc interfered with copper absorption at the intestinal level. The data presented here demonstrated that there was a significant decrease in copper content with a concomitant increase in zinc content of the intestinal segment of the zinc-fed rats. Gel filtration analysis on Sephadex G-75 of the cytosol fraction from the mucosa of the zinc-fed rats demonstrated that major parts of zinc in the cytosol bind to the protein with a molecular weight of about 10000, that is, the zincthionein. The simultaneous administration of copper and zinc to the normal rats also caused an incorporation of copper into this protein. These results suggested that the interference of copper absorption by zinc may be due to the inductive effect of zinc on the synthesis of the zinc-thionein, which sequesters copper available for absorption.

Inhibitory effect of high dietary zinc on copper absorption in rats.

High dietary zinc resulted in the lowering of growth, hemoglobin concentration, ceruloplasmin activity and copper concentration in liver, kidney and serum with a marked increase in the concentration of zinc in these tissues. The preliminary experiments were made to determine the sites at which zinc interferes with copper metabolism. When copper was administered to the zinc-fed rats either orally or intraperitoneally, the depression in copper uptake into liver was clearly observed in the former case. Moreover, copper uptake into liver was depressed even when both copper and zinc were administered orally to the normal rats. By the short-period experiments using 64Cu, it was also shown that zinc interferes with the absorption and utilization of copper. These results indicate that the interference of copper metabolism by zinc feeding is mainly due to the inhibition of copper absorption at the intestinal level.

Zinc Interference with Copper Absorption in Rats

A study was made to determine the site or sites at which zinc interferes with the intestinal absorption of copper. 64Cu was administered to all rats via ligated, in vivo, segments of duodenum, and zinc was administered either intraduodenally or intraperitoneally. High levels of zinc depressed the absorption of 64Cu when both the zinc and the 64Cu were placed directly into the isolated segment. If the 64Cu was put into the intestinal segment and the zinc was given intraperitoneally, no depression in 64Cu absorption resulted. However, the rats given intraperitoneal injections of zinc had tissue zinc concentrations that were comparable to those of rats given zinc intraduodenally. These results indicate that zinc does not depress copper absorption by first building up to critical levels in some non-intestinal tissue or tissues and, subsequently, interfering with copper absorption. Rather, the evidence indicates that the depression of copper absorption by high levels of zinc is mediated either in or on the intestine.