| Background:Deltamethrin (deltamethrin, DM) belonging to the type ofâ…¡pyrethroid (Synthetic pyrethroids, SPs) insecticide, is one of the largest toxicity pesticides in the synthetic pyrethroid insecticide controlling pests in cotton, vegetable, fruit, tea and mothes in experiment samples. It is considered low toxic and more safe pesticides because of it is susceptible to degradate by enzyme system and no accumulation. Most mosquito repellents,air freshener and cockroachkillers are pyrethroid pesticides.With the SPs widely using, it was concerned in poison by mis-use or polluting food causing environment problems, especially it is a nerve toxic activity that it can act on the nerve membrane, change permeability of the nerve membrane and disturbance the nerve conduction. The toxicity of deltamethrin is mainly on the central nervous system of the mammalian and their important toxic symptoms are:tremor and salivation. The study about the toxicity of deltamethrin refer to the acute and subacute toxicity on the mammalian and aquatic animal (i.e.fish).Object: To explore the chronic toxicity of deltamethrin on rats gastric mucosa injury and expression of substance P in the gastric mucosa.Methods:Wistar rats (No.=32), male and female, weighting 120g-150g (Laboratory Animal Center,Qingdao)were randomly divided four groups and each group contained eight rats. Wistar rats were given different doses of deltamethrin dissolved in the olive oil via esophagus: low-dose group(1.5625 mg/kg), mid-dose group(3.1250 mg/kg), high-dose group(6.2500 mg/kg), but the control group received olive oil only. The dosage of standard was 5ml/kg. DM dissolved in olive oil was administered to rats through esophagus at AM 9:00 every day, for 24 weeks. The body weight was measured every week before administration of DM. Twenty-four weeks later, rats fasted overnight were anaesthetized with 8% Chloral Hydrate (5ml/kg). Paraffin sections were made from the fundus of stomach. After HE and immunohistochemical staining, the degrees of gastric mucosa injury and the expression of substance P were observed.Results:Gastric mucosa of the control group was looked normal and integrated, fundic glands was regular, parietal cells were normal and no inflammation cells were found by light microscopic observation. However, gastric mucosa of deltamethrin treated rat shown different degrees of lesions on the basis of different dosages. Compared with those of other groups, the degrees of gastric mucosa damage in high-dose group were notably higher (P<0.05) and the number of parietal cells in high-dose group was significantly higher too (P<0.05). Expression of substance P was found in cells of the rat gastric mucosa in all groups with the weak expression found in the control group. The average optical density (OD) values found in the high and middle dose groups were significantly higher than those of another groups (P<0.05).Conclusion:Deltamethrin has apparently chronic harmful effects on rats'gastric mucosa injury especially the number of the parietal cells in the fundic gland is increasing according to the different of dosage. The number of the parietal cells in the high group is higher than the another group, and compared the control group the number of the parietal cells is significant on satistics. The mechanisms may be relate to the damage of stomach mucosa barrier,gastric mucosal blood flow,the changes of hormone in stomach and SP may be involved in the pathogenesis of the localized gastric lesions.
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