Tissue-Specific Accumulation of Metallothionein in Chickens as Influenced by the Route of Zinc Administration

Abstract

The effect of the route of zinc (Zn) administration on the induction of metallothionein (MT) in various tissues of chicks was examined. Four-week-old, male chicks were assigned to one of four treatments: 5 mg Zn/kg intraperitoneal (i.p.) injection, 5 mg Zn/kg intravenous (i.v.) injection, 16 mg Zn oral (O) dose or a saline control (C). Chicks were fasted overnight, treated and killed 24 h later. 109Cd radioassay analysis of liver (L), kidney (K) and pancreas (P) showed a significant elevation of MT in all tissues except K of i.v. chicks. Comparing tissue MT accumulation within treatments showed that L was induced to a greater extent than P for the i.p. treatment (P/L ratio = 0.69 +/- 0.04), while the reverse effect was seen for both O (1.51 +/- 0.10) and i.v. (1.67 +/- 0.14) chicks, reflecting greater P than L accumulation. Zn injected i.p. did not result in significantly greater total peritoneal exudate cell (PEC) or macrophage (M) numbers than saline-injected controls. Sephadex, while causing massive increases in PEC and M, did not induce tissue MT, demonstrating the lack of correlation between PECs or Ms and MT accumulation. Feed intake by chicks during the 24-h period following i.p. Zn treatment was only 30% of that by controls. A subsequent experiment demonstrated that a similar restriction in feed intake increased L but not P MT. This increase accounted for 17.8% of the L induction due to i.p. Zn injection. This does not fully account for the reduction in P/L that is characteristic of i.p. treatment.(ABSTRACT TRUNCATED AT 250 WORDS)