Abstract
Lead- (Pb-) induced oxidative stress is known to suppress growth performance and feed efficiency in broiler chickens. In an attempt to describe the specific underlying mechanisms of such phenomenon we carried out the current study. Ninety-six one-day-old broiler chicks were randomly assigned to 2 dietary treatment groups of 6 pen replicates, namely, (i) basal diet containing no lead supplement (control) and (ii) basal diet containing 200 mg lead acetate/kg of diet. Following 3 weeks of experimental period, jejunum samples were collected to examine the changes in gene expression of several nutrient transporters, antioxidant enzymes, and heat shock protein 70 (Hsp70) using quantitative real-time PCR. The results showed that addition of lead significantly decreased feed intake, body weight gain, and feed efficiency. Moreover, with the exception of GLUT5, the expression of all sugar, peptide, and amino acid transporters was significantly downregulated in the birds under Pb induced oxidative stress. Exposure to Pb also upregulated the antioxidant enzymes gene expression together with the downregulation of glutathione S-transferase and Hsp70. In conclusion, it appears that Pb-induced oxidative stress adversely suppresses feed efficiency and growth performance in chicken and the possible underlying mechanism for such phenomenon is downregulation of major nutrient transporter genes in small intestine.
Highlights
Lead (Pb) is one of the widespread environmental pollutants that induce a broad range of physiological and biochemical dysfunctions in animals [1]
Several researchers suggested that the biochemical and molecular mechanism of Pb toxicity involve the induction of oxidative stress in target cells and generation of reactive oxygen species (ROS), followed by DNA damage and apoptosis partly via the (1) direct effect of Pb on cell membranes, (2) Pb-hemoglobin interactions, (3) consistent reduction in blood delta-aminolevulinic acid dehydratase (ALAD), an erythrocyte enzyme sensitive to Pb, and (4) effect of Pb on antioxidant defense systems of cells [8,9,10,11,12,13]
The mRNA expressions of all studied sugar transporters except GLUT5 were significantly downregulated in Pbexposed chicks (Figure 4)
Summary
Lead (Pb) is one of the widespread environmental pollutants that induce a broad range of physiological and biochemical dysfunctions in animals [1]. Mahesar et al [2] reported that most of the poultry feed samples which they analyzed contained greater amount of Pb and cadmium (Cd) than the maximum tolerable levels for poultry. This observation suggests the possibility of accumulation of Pb in commercially produced poultry meat and meat products. Varying levels of ROS may impact mRNA and protein expression [15] These changes are elicited primarily by transcriptional and posttranscriptional mechanisms via alterations in chromatin metabolism and transcription factors activity [16] and RNA-binding proteins and microRNAs [17,18,19].
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