[Biological monitoring of workers exposed to trimethyltin chloride]

OBJECTIVE

To investigate suitable biomarkers for workers exposure to trimethyltin chloride (TMT-cl).

METHODS

Urinary samples of 44 male workers from five TMT-cl occupational poisoning incidents were collected. Methyltin mercaptide stabilizers and waste plastics used in the incidents were also collected. The levels of TMT-cl in all the samples were determined by gas chromatography. The concentration of blood potassium for each poisonings was determined compared to control group (50 male workers of a food company), and the correlation between blood potassium and urinary TMT-cl were also determined.

RESULTS

TMT-cl was detected in urine of all the poisonings. The results were (0.869 +/- 0.392) microg/L (severe poisoning), (0.963 +/- 0.482) microg/L (moderate poisoning), (0.716 +/- 0.384) microg/L (mild poisoning) respectively and the difference was statistically significant (P < 0.01). But the severity of the clinical status did not seem to be closely correlated to the level of urinary TMT-cl (F = 1.88, P > 0.05). In the severe poisonings, there were no differences in urinary TMT-cl on day 4 after poisoning from day 1 (P > 0.05). In contrast, urinary TMT-cl was decreased significantly on day 4 than on day 1 in mild and moderate poisonings (P < 0.01). On day 21, levels of urinary TMT-cl of all the poisonings were higher than those of the workers exposed to TMT-cl who had no clinical status (P < 0.01). Blood potassium levels of exposed group was 77.3% which was significantly lower than normal value (P < 0.01). The concentration of blood potassium was lower than normal value (3.5 mmol/L) and was correlated with the severity of the clinical status (F = 4.45, P < 0.05). Level of urinary TMT-cl of exposed group was negatively correlated with blood potassium (r = -0.4456, P < 0.01).

CONCLUSION

Level of urinary TMT-cl can be used as exposure biomarker of TMT-cl poisoning. Blood potassium is an early biomarker of effect for TMT-cl poisoning so as to find poisoning population early.

Studies on hypokalemia induced by trimethyltin chloride

OBJECTIVES

To determine the possible relationship between plasma potassium concentration and severity of acute trimethyltin chloride (TMT) poisoning and to assess the mechanism of TMT induced hypokalemia.

METHODS

SD rats were treated with various dosages of TMT (i.p.). All the indices were measured and analysed for determining their possible relations with plasma K+.

RESULTS

With increase of dosage, the plasma K+ level dropped rapidly, and deaths appeared more quickly. The LD50 of TMT (i.p.) was 14.7 mg/kgbw. In the low dosage group (10 mg/kgbw), the plasma K+ level dropped slowly with the lowest dosage on day 6 (4.85 mmol/L). It rose again on day 11 (5.06 mmol/L), and recovered on day 28. The poisoning signs corresponded with decline of the span of K+ level. The plasma Na+ level dropped half an hour after TMT treatment, but recovered 24 h later. In the high dosage group (46.4 mg/kgbw), the levels of plasma K+ and Na+ fell rapidly within half an hour (P < 0.05), the intracellular potassium concentration of RBC did not decrease obviously (P > 0.05), the activities of Na(+)-K(+)-ATPase and Mg(2+)-ATPase in RBC membrane were depressed remarkably (P < 0.01, P < 0.05, respectively), the plasma aldosterone concentrations rose as high as tenfold (P < 0.01), the arterial blood pH fell from 7.434 to 7.258 (P < 0.01), pCO2 was raised from 29.62 to 45.33 mmHg (P < 0.01). In the 24 h urine test, when rats were treated with TMT (21.5 mg/kgbw, i.p.), urine volume, urinary potassium, sodium and chloride increased significantly in comparison with those in the controls (P < 0.01).

CONCLUSION

TMT could induce hypokalemia in SD rats. The available evidence suggests that TMT can induce acute renal leakage of potassium. At the same time, a significant rise of plasma aldosterone may play an important role in promoting potassium leakage from kidney to result in severe hypokalemia with inhaling acid-base abnormalities produced, which aggravate the poisoning symptoms. In the end the rats would die of respiratory failure.

Temporal change of hippocampal enkephalin and dynorphin mRNA following trimethyltin intoxication in rats: effect of anticonvulsant

Trimethyltin (TMT), an organic metal, has been known to induce behavioral abnormalities including seizures and aggression. We administered TMT to rats, then, behavioral changes as well as the changes of dynorphin and Met-enkephalin mRNA were observed with or without phenobarbital treatment in order to reveal the role of neuropeptides in seizure-generating mechanisms. Met-enkephalin mRNA was significantly increased at the 2nd to 6th day after TMT administration when seizure was frequently observed. Meanwhile, dynorphin mRNA was decreased significantly from the 2nd day to 16th day during aggression score remained high. Phenobarbital abolished not only seizures and aggression, but also the changes of neuropeptide expressions. These results suggest that the changes of dynorphin mRNA are more strongly associated with aggression than seizures, while Met-enkephalin changes correlate more with seizures.

Trimethyltin intoxication induces marked changes in neuropeptide expression in the rat hippocampus

In situ hybridization and immunocytochemistry were applied to investigate changes in the expression of somatostatin, neuropeptide Y, neurokinin B, cholecystokinin, dynorphin, and Met-enkephalin in the rat hippocampus after administration of a single peroral dose of trimethyltin hydroxide (9 mg/kg). Two time intervals were investigated: 5 days after trimethyltin treatment, when CA3 damage becomes manifest and is associated with increased aggression, seizure susceptibility, and memory deficit, and 16 days after trimethyltin, when neuronal damage is almost maximal and seizure susceptibility is declining. Robust but transient increases of neuropeptide Y, neurokinin B, and Met-enkephalin mRNA levels were revealed in the granule cell layer of the dentate gyrus and increased neuropeptide Y and neurokinin B immunoreactivities were found in mossy fibers. In reverse, dynorphin mRNA and immunoreactivity were decreased transiently in the dentate gyrus and mossy fibers, respectively. Strong over-expression of NPY mRNA was also observed in hilar interneurons and in CA1 and CA3 pyramidal cells as well as in the cortex at 5 days postdosing. Cholecystokinin- or neurokinin B-containing basket cells were preserved, while somatostatin-bearing interneurons were damaged by trimethyltin exposure. These neurochemical changes induced by trimethyltin intoxication strikingly parallel to those observed in animal models of temporal lobe epilepsy and may reflect activation of endogenous protective mechanisms. It is also suggested that hilar interneurons respond differently to trimethyltin exposure, for which neuropeptides are valuable markers.

Nitric oxide synthase-containing neurons in the hippocampus are preserved in trimethyltin intoxication

We studied the effects of trimethyltin (TMT) (9 mg/kg, p.o.) on the nitric oxide synthase (NOS)-containing neurons in the rat hippocampus by NADPH-diaphorase histochemistry and a biochemical assay of NOS activity. TMT exposure caused the typical behavioral changes and a loss of the CA3/4 pyramidal cells, which were NADPH diaphorase-negative. The scattered interneurons and the CA1 pyramidal cells, which were NADPH diaphorase-positive, were spared. Hippocampal NOS activity showed no reduction in the TMT-treated rats compared with the controls. These results provide evidence of the preservation of the NOS-containing neurons in TMT intoxication.

Changes in muscarinic (M1 and M2 subtypes) and phencyclidine receptor density in the rat brain following trimethyltin intoxication

The main purpose of this study was to determine whether one or both of the muscarinic receptor subtypes (M1 and M2) contributed to the total cholinergic receptor loss found in trimethyltin (TMT) treated rats and to assess the effect of TMT on phencyclidine (PCP) receptor density in several regions of the rat brain. The distribution and changes in muscarinic (M1 and M2) receptor and PCP receptor sites were analysed by means of quantitative autoradiography using [3H]quinuclidinyl benzilate (QNB) and [3H] N-(1-(2-thienyl) cyclohexyl) 3,4-piperidine (TCP) respectively. The results demonstrate a TMT induced decrease in [3H]QNB binding in a large number of brain regions particularly the hippocampal formation, for both M1 and M2 muscarinic receptor subtypes. There is also a decrease in [3H]TCP binding in several brain regions. The effects of TMT on PCP receptors suggest that TMT induced damage is not restricted to the cholinergic system and that N-methyl-D-aspartate (NMDA) receptors are also affected.

Trimethyltin poisoning: report of a case with postmortem examination

A 48-year old woman died six days after intake of an unknown amount of trimethyltin (TMT). Early clinical features were tinnitus, lightheadedness, aggression and episodes of unresponsiveness. She gradually developed coma and died of multiorgan failure. The main pathologic findings were confined to the nervous system which revealed generalized chromatolysis of the neurons in the brain, spinal cord and spinal ganglia. Recent neuronal necrosis, which probably was caused by toxic effect of TMT, was present in the fascia dentata of the hippocampus and in the spinal ganglia. Recent necrosis was also present in the pyramidal cell layer of the hippocampus, cerebral cortex, basal ganglia and Purkinje cell layer of the cerebellum, but some of these changes could have been caused by an anoxic episode shortly before death. Electron microscopy revealed marked accumulation of lysosomal dense bodies and disorganization of the granular endoplasmic reticulum in the neurons. The findings were similar to those described in experimental TMT intoxications. Cytoplasmic zebra bodies, which were described in a previous human case of TMT intoxication, were not observed in the present case.

Acute short-term memory loss from trimethyltin exposure

We report a case of organic tin exposure in a graduate chemistry student. The inhalational and transcutaneous exposure occurred following a laboratory explosion. The patient initially presented with first and second degree burns of the face and chest, and developed an acute loss of short-term memory 72 hours after exposure. The memory loss gradually improved over the course of several months.

Neuropathology of trimethyltin intoxication. IV. Changes in the spinal cord

Young C57BL/6N mice were injected (ip) with trimethyltin chloride at a dosage of 3.0 mg/kg body wt. Animals were sacrificed between 48 to 72 hr postinjection by means of intracardial perfusion of saline solution followed by 2.5% buffered glutaraldehyde. For light microscopy, the cords were further fixed in 10% buffered formalin and embedded in Paraplast. For electron microscopy, tissue samples were obtained from the cord levels at L1-L4, further fixed in glutaraldehyde and osmium tetroxide, and embedded in Epon. Chromatolytic and vacuolar changes involving neurons mainly in the medial and lateral motor nuclei of the anterior horns were observed. Electron microscopy revealed lysosomal accumulation and extensive dilatation of the cytoplasmic membrane systems (endoplasmic reticulum, Golgi complex). Large intraneuronal vacuoles were formed as a result of extensive intraneuronal edema. Progressive distention of the cytoplasmic membranes resulted in severe vacuolation, disintegration, and total breakdown of the neurons.

The behavioral and neuropathologic sequelae of intoxication by trimethyltin compounds in the rat

Trimethyltin, when given by gavage to rats, has an LD50 of 12.6 mg/kg. Signs of poisoning include tremors, hyperexcitability, aggressive behavior, weight loss, and convulsions. After single (10 mg/kg) or repeated weekly doses (a maximum of four) of 4 mg/kg, rats, up to a survival time of 70 days, were perfusion-fixed for light microscopy. Trimethyltin was assayed in brain and blood in rats after similar treatments. Trimethyltin is cumulative and persistent and binds with high affinity to hemoglobin. Trimethyltin, unlike triethyltin, does not produce white matter edema in rats but does cause bilateral and symmetrical neuronal alterations involving the hippocampus (largely sparing the Sommer sector), pyriform cortex, amygdaloid nucleus, and neocortex. The earliest alteration was loss or dispersal of Nissl substance, then clumping of nuclear chromatin, followed by shrinkage and fragmentation of the nucleus within shrunken eosinophilic cytoplasm. These changes were associated with approximately 1.4 microgram trimethyltin/g wet weight in brain tissue 1 day after the second dose of 4 mg/kg or 2 days after a single dose of 10 mg/kg. Signs of poisoning gradually disappeared, and 4 rats surviving 70 days appeared normal, although their brains had severe damage with cell loss in the hippocampi and each pyriform cortex. Treatment of rats with trimethyltin, therefore, provides a chronic preparation with consistent lesions in the hippocampus of use in other behavioral and neuroanatomic studies. (Am J Pathol 97:59--82, 1979).