| Objective To discuss the biological effects induced by trimethyltin chloride (TMT) poisoning in rats at different time-points through the indicators of tissue homogenate, the observations on overall animals and pathological changes, and then to speculate the mechanism of central nervous system injury induced by TMT intoxication.Methods (1) Improvement of the techniques and the basic conditions for the experiments required . For selecting a better method for collecting cerebrospinal fluid in SD rats, 30 male SD rats were randomly divided into 3 groups. Cerebrospinal fluid (CSF) in the rats was respectively drawn by 3 methods, cerebrospinal fluid from cerebellomedullary cistern via percutaneous puncture, gashed spinal dura mater under direct vision,and the using micro injector via spinal dura mater puncture under direct vision. The collection volumes and the pass rates of successful collection among 3 methods were compared. The animal models of TMT intoxication were made by treating SD rats with 10.0mg/kg (i.p.) TMT. 36 female SD rats were randomly divided into 6 groups. The levels of K+ in plasma were determined after 1 h, 12 h, 24 h, 48 h and 72 h. Successful animal models of TMT intoxication in different periods were judged if the K+ levels matched with the psychotic symptoms of the poisoned animals. (2) The effects of TMT on inhibiting the activity of Na+- K+- ATPase (NKA) in choroid plexus of rats in vitro. Through the comparison to the effects of the activities of NKA in choroid plexus in vitro induced by different concentrations of TMT and by ouabain, a positive control material, the specific damage of NKA in choroid plexus elicited by TMT was analyzed. (3) Effects of TMT on the activity of NKA in choroid plexus and on cerebrospinal fluid of rats in vivo. 36 female SD rats were randomly divided into 6 groups. Cerebrospinal fluid and plasma of the control group, group 1h, group 12h, group 24h, group 48h and group 72h were collected and determined after treated with TMT at 10.0 mg / kg (i.p.), to assess the influence of TMT on the cerebrospinal fluid and plasma. The homogenates of the choroid plexus tissues, brains, kidneys and livers of all above groups were preparated, and then changes caused by TMT intoxication were observed through the activities of NKA and H+-K+-ATPase (HKA) were measured. (4) Pathological changes in brain tissues of the control group, group 1h, group 12h, group 24h, group 48h and group 72h were observed after treated with TMT at 10.0 mg / kg (i.p.). Data were analyzed by ANOVA, t test or rank sum test with SPSS13.0.Results (1) The collection volume and the pass rate with the method of using micro injector via spinal dura mater puncture under direct vision was much larger or higher than those of the following methods, the cerebrospinal fluid from cerebellomedullary cistern via percutaneous puncture and gashed spinal dura mater under direct vision, and the differences were statistically significant (P<0.01). After the rats were exposed to 10.0 mg / kg (i.p.) TMT, there were some psychiatric symptoms appeared on the animals. Compared with that of the control group, the levels of plasma K+ in group 1h, group 12h, group 24h, group 48h and group 72h showed a significant decrease (P <0.05 or P <0.01). (2) In vitro, both ouabain and TMT could inhibit the activity of NKA. And along with the increase of the doses, the inhibition increased gradually. (3) Experience in vivo:①After TMT exposure, animals were seen hypopraxia, bad spirit, and felling down. Most animals appeared strong poisoning symptoms about 30h later, irritability, attacking, and worrying , and a few animals were observed convulsions with salivation, tremors and unsteady gait;②Compared with that of the control group, the levels of cerebrospinal fluid K+ of the group 1h, group 12h, group 24h, group 48h and group 72h were shown a significant decrease (P<0.05 or P<0.01), while the levels of GLU were increased;③Similarly, compared with that of the control group, group 12h, group 24h, group 48h and group 72h, the levels of cerebrospinal fluid K + were shown a significant decrease (P <0.05 or P <0.01);④After TMT exposure, the NKA activities of choroid plexus tissue homogenate in the group 1h, group 12h, group 24h, group 48h and group 72h were decrease significantly (P <0.01) compared with the control group, and the activity inhibition increased gradually with the prolonging of the exposure time;⑤Compared with those of the control group, the NKA and HKA activities in liver and renal homogenate, the HKA activity in brain homogenate were decrease significantly (P <0.05), and they declined gradually with the longer exposure time. (4) Pathological findings: There was no obvious abnormal change in brain pathology examination of all above animals with light microscopy.Conclusion We preliminarily proved that the inhibition of NKA activity in choroid plexus cavity membrane surface induced by TMT was related to the mechanism of central nervous system damage induced by TMT, and found the evidence for the hypothesis that the mechanism of TMT poisoning was the inhibition of the activity of cavity membrane surface ATPases. |
