OBJECTIVETo study influence of lanthanum chloride (LaCl(3)) on the expression of immediate early genes (IEGs) including c-jun, early growth response gene 1 (Egr1) and activity-regulated cytoskeletal gene (Arc) in the hippocampus of rats, and discuss the mechanism of LaCl(3) undermining learning and memory capability.

METHODSForty female Wistar adult rats were divided into control group, low LaCl(3)-contaminated group (0.25%), medium LaCl(3)-contaminated group (0.50%), and high LaCl(3)-contaminated group (1.00%) by randomized design. Each group had ten female rats along with five male rats and mated by the ratio of 2:1. The amounts of pups in the above four groups were 80, 83, 78 and 75 separately. The pups in respective group were La-dyed by lactation, and then the pups in LaCl(3)-contaminated groups drank 0.25%, 0.50% and 1.00% LaCl(3) separately for one month. Learning and memory capability of pups were measured in jumping stairs experiment. Hippocampal lanthanum content was determined by inductively coupled plasma mass spectrometry (ICP-MS). Hippocampal c-jun, Egr1 and Arc mRNA expression was detected by RT-PCR, and corresponding protein expression was measured by Western blotting method.

RESULTSIn the jumping stairs experiment, pups in 0.25%, 0.50% and 1.00% LaCl(3)-contaminated groups respectively made (1.75 ± 0.71), (2.38 ± 0.92) and (3.00 ± 0.76) mistakes; significantly higher than control group (1.25 ± 0.46) (q values were 4.386, 6.793, P < 0.05). However, the incubation period of 0.25%, 0.50% and 1.00% LaCl(3)-contaminated groups were (174.13 ± 33.72), (139.25 ± 45.83) and (75.50 ± 18.56) respectively, which were all significantly lower than that of control group (206.75 ± 20.47) (q values were 2.958, 6.121, 11.902, P < 0.05). Hippocampal c-jun mRNA expression were (0.89 ± 0.08), (0.77 ± 0.12), (0.58 ± 0.14) and (0.29 ± 0.10); while the c-jun protein expression were (0.72 ± 0.13), (0.64 ± 0.11), (0.43 ± 0.11) and (0.31 ± 0.14), and the Egr1 mRNA expression were (0.78 ± 0.09), (0.61 ± 0.13), (0.53 ± 0.10) and (0.22 ± 0.08), Egr1 protein expression were (0.65 ± 0.18), (0.40 ± 0.15), (0.32 ± 0.13) and (0.14 ± 0.09) in 0.25%, 0.50% and 1.00% LaCl(3)-contaminated groups; and all of which presented a dose-effect relationship that the correlation coefficients of these parameters with dose were -0.900 (t = 11.309, P = 0.000), -0.969 (t = 7.058, P = 0.000), -0.898 (t = 11.179, P = 0.000) and -0.962 (t = 6.739, P = 0.000).

CONCLUSIONLaCl(3) undermines the learning and memory capability of rats, which is possibly related to lower expression of c-jun and Egr1 gene and protein induced by lanthanum in hippocampus.