The involvement of metallothionein in hepatic and renal Cd, Cu and Zn accumulation in pigs

Abstract

a b s t r a c tThis study investigated the involvement of metallothionein (MT) in hepatic and renal cadmium (Cd) accumulation and the interactions of this element with the essential elements copper (Cu) and zinc (Zn) in pigs receiving diets with or without Cu and Zn supplementation, in intensive and extensive production systems respectively. Animals from intensive systems showed significantly higher Cd concentrations in the liver (83.3 mg/ kg wet weight) and kidney (343 mg/kg) than animals from extensive systems (33.2 and 130 mg/kg respectively). Cu (liver 16.9, kidney 5.52 mg/kg) and Zn (82.8 and 29.7 mg/kg) concentrations were also significantly higher in pigs from intensive than in animals from extensive systems (Cu 10.1 and 4.64 mg/kg, Zn 66.2 and 23.1 mg/kg). Pigs from intensive systems showed 50% higher kidney MT concentrations than animals from extensive systems (278 and 183 mg/kg respectively), whereas liver MT concentrations were very similar in the two groups (1696 and 1517 mg/kg respectively). MT concentrations in both the liver and the kidney were strongly dependent on the Zn status of the animal. In the liver neither Cu nor Cd displaced Zn from MT, and the proportion of MT binding sites apparently occupied by Cu and Cd decreased with increasing hepatic MT concentration, despite the fact that both Cu and Cd have higher affinity for MT than Zn. The proportion of MT binding sites occupied by Cu and Cd was also directly related to Zn:Cu ratio in hepatic cells. In the kidney, in contrast, Cu seems able to compete with Zn for MT binding sites, and the proportion of MT binding sites occupied by Cu increased with increasing renal MT concentration.

Fluctuation of potential zinc status biomarkers throughout a reproductive cycle of primiparous and multiparous sows

“…Plasma Cu can be bound to MT as well, but fluctuations in plasma Cu concentration in the present study are comparable with other studies in sows ( 29 , 33 ) , women ( 35 ) and ewes ( 36 ) , and therefore suggests that plasma Cu was not interfering with the fluctuation of serum MT. This was also observed in the study by López-Alonso et al ( 37 ) , where liver and kidney MT concentrations were highly dependent on the Zn status of the pig, and neither Cu nor Cd displaced Zn from MT.…”

Dietary Zinc Supplementation to Prevent Chronic Copper Poisoning in Sheep

“…It is known that (i) the marked inter-species differences in terms of susceptibility to hepatic Cu toxicity is related to the ability to synthesize hepatic MT [38,39], and (ii) Zn is a potent inductor of MT in the liver with hepatic MT concentrations being strongly related to the hepatic Zn [27]. However, hepatic MT induction does not seem to be the primary mechanism by which Zn exerted protection against hepatic Cu accumulation in the present study.…”

Trace Minerals and Livestock: Not Too Much Not Too Little

“…This is especially relevant for pigs, where trace minerals and Zn are used at very high concentrations as growth promoters and have a very high capacity to induce metallothioneins [55]; for example Cd residues in the liver and kidney were double in animals receiving 200 mg trace minerals/kg DM for three months compared to the controls [56]. Recent studies in our laboratory indicate that hepatic and renal Cd accumulation was significantly higher in pigs from intensive systems (Cu and Zn supplemented) compared with extensively grown animals (no supplemented) which was related to the metallothionein induction by the former trace mineral [57, 58]. …”