Table 7.

Effect of lead nitrate on gene expressions of antioxidant enzymes and Nrf2–Keap1 molecules in the ovary of laying hens.¹

Item2	Dietary Pb concentration (mg/kg)				P-value	SEM	Contrast P-value
	3.20	33.20	63.20	93.20			L	Q
CuZnSOD	0.99a	0.80b	0.55c	0.37d	<0.01	0.03	<0.01	0.76
MnSOD	0.96	0.91	0.99	1.01	0.68	0.08	0.39	0.57
CAT	1.00a	0.75b	0.51c	0.33d	<0.01	0.05	<0.01	0.29
GR	1.11a	0.79b	0.48c	0.46c	<0.01	0.06	<0.01	0.03
GSH-Px	1.09a	0.53b	0.56b	0.45b	<0.01	0.06	0.01	<0.01
Nrf2	1.37a	0.78b	0.54c	0.39d	<0.01	0.05	0.01	<0.01
Keap1	0.75d	1.22c	1.63b	2.16a	<0.01	0.11	<0.01	0.73

Abbreviations: CAT, catalase; CuZnSOD, copper–zinc superoxide dismutase; GR, glutathione reductase; GSH-Px, glutathione peroxidase; Keap1, Kelch-like ECH-associated protein 1; MnSOD, manganese superoxide dismutase; Nrf2, nuclear factor erythroid 2–related factor 2; Pb, plumbum.

¹Means within each row with different superscripts were significantly different (P < 0.05). SEM: standard error of the mean by ANOVA (n = 6); L: linear; Q: quadratic.

²Regression equation of CuZnSOD, y = 1.207–0.213x, R² = 0.948; regression equation of CAT, y = 1.213–0.227x, R² = 0.899; regression equation of GR, y = 1.280–0.228x, R² = 0.806; regression equation of GSH-Px, y = 1.695–0.755x + 0.113x², R² = 0.790; regression equation of Nrf2, y = 2.110–0.862x + 0.109x², R² = 0.952; regression equation of Keap1, y = 0.276 + 0.465x, R² = 0.902.