Tissue-specific variations in the induction of Hsp70 and Hsp64 by heat shock in insects

Effect of manganese on heat stress protein synthesis of new-born rats

AIM: To study the effect of manganese (Mn) on heat stress protein 70 (HSP70) synthesis in the brain and liver of new-born rats whose mother-rats were exposed to Mn.

METHODS: 32 female rats were randomly divided into four groups. One group was administrated with physiological saline only as control group, the other three groups were administrated with 7.5, 15 and 30 mg·kg^-1 manganese chloride (MnCl₂) by intraperitioneal injection every two days for two weeks. After delivery, the mother-rats received MnCl₂ unceasingly for a week with the same method. Then the contents of Mn, Zn, Cu and Fe in the livers of the new-born rats were determined by atomic absorption spectroscopy; The level of HSP70 in the brains and the livers of the new-born rats as detected by Western-dot-blotting, and the SOD activities were measured simultaneously.

RESULTS: The contents of Mn in the livers of new-born rats of the experimental groups (respective 1.38 ± 0.18, 2.73 ± 0.65, 3.44 ± 0.89 μg·g^-1) were significantly increased compared with the control group (0.88 ± 0.18 μg·g^-1; P < 0.01); The contents of Fe in the livers of new-born rats of 15 and 30 mg·kg^-1 experimental groups (426 ± 125, 572 ± 175 μg·g^-1, respectively) were significantly increased compared with the control group(286 ± 42 μg·g^-1;P < 0.05); the levels of Zn in the livers of the new-born rats of three experimental groups(254 ± 49, 263 ± 47, 213 ± 28 μg·g^-1, respectively) were lower than those of the control group (335 ± 50 μg·g^-1; respective P < 0.05, P < 0.01); and the levels of Cu showed no significant difference among the four groups (three experimental groups: 75 ± 21, 68 ± 241 and 78 ± 18 μg·g^-1; control group: 83 ± 9 μg·g^-1; P > 0.05). There was a significant increase in the levels of HSP70 in the brains of new-born rats of the 30 mg·kg^-1 group (19.5 × 10³± 1.3 × 10³ A; control group: 14.3 × 10³± 1.4 × 10³A; P < 0.01),and the levels of HSP70 in the livers of new-born rats of three experimental groups(respective 19.6 × 10³± 3.9 × 10³A, 18.5 × 10³± 3.8 × 10³A, 22.4 × 10³± 1.9 × 10³A) also increased than control group(13.3 × 10³± 1.0 × 10³A; P < 0.01), but the SOD activities showed no significant difference among brains of the four groups (experimental groups: 5.04 ± 0.43, 4.83 ± 0.48, 4.60 ± 0.84 ku·g^-1; control group: 4.91 ± 0.37 ku·g^-1; P > 0.05). The SOD activities in the livers of 15 mg·kg^-1 group (5.41 ± 0.44 ku·g^-1) was lower than the control group(5.95 ± 0.36 ku·g^-1; P < 0.05).

CONCLUSION: While mother-rats were exposed to manganese, the metabolisms of Mn, Zn and Fe of new-born rats in the livers were influenced and were situated in a stress status, thus HSP70 syntheses is induced in the brains and livers of new-born rats, but the mechanism of this effect in the developmental toxicity of Mn remains to be further studied.