Trichloroethylene and halothane inhibit uptake and metabolism of 5-hydroxytryptamine in rat lung slices

Urinary trichloroacetic acid and high blood pressure: A cross-sectional study of general adults in Shijiazhuang, China

Exposure to trichloroacetic acid (TCAA) and its parent chemicals potentially linked to cardiovascular disease. However, the association between TCAA and blood pressure (BP) has not been studied to date. The purpose of this study was to examine the potential association between urinary TCAA levels and BP in a Chinese population. We measured BP parameters (including systolic BP, diastolic BP and pulse pressure) and TCAA concentrations in the urine of 569 adults from a primary health care clinic in Shijiazhuang, China. Logistic and linear regressions were used to investigate the relationships between the urinary TCAA levels and BP parameters. To evaluate the robustness of the results, we conducted sensitivity analyses by re-analysing data after excluding urine samples with extreme specific creatinine values. We found that urine TCAA levels were positively associated with systolic BP and pulse pressure based on trend tests after adjusting for potential confounders (both p for trend < 0.05). Finally, only the association of TCAA with systolic BP remained significant in the sensitivity analyses (p < 0.05). Our results suggested that TCAA exposure was associated with increased BP in adults. Because urinary TCAA has been proposed as a valid biomarker of disinfection by-product (DBP) ingestion through disinfected drinking water, our results further suggest that exposure to drinking water DBPs may contribute to high BP in humans. Additional research is needed to confirm these findings and to evaluate opportunities for intervention.

Respiratory effects of trichloroethylene

Trichloroethylene (TCE) is a chlorinated solvent that has been used widely around the world in the twentieth century for metal degreasing and dry cleaning. Although TCE displays general toxicity and is classified as a human carcinogen, the association between TCE exposure and respiratory disorders are conflicting. In this review we aimed to systematically evaluate the current evidence for the respiratory effects of TCE exposure and the implications for the practicing clinician. There is limited evidence of an increased risk of lung cancer associated with TCE exposure based on animal and human data. However, the effect of other chlorinated solvents and mixed solvent exposure should be further investigated. Limited data are available to support an association between TCE exposure and respiratory tract disorders such as asthma, chronic bronchitis, or rhinitis. The most consistent data is the association of TCE with autoimmune and vascular diseases such as systemic sclerosis and pulmonary veno-occlusive disease. Although recent data are reassuring regarding the absence of an increased lung cancer risk with TCE exposure, clinicians should be aware of other potential respiratory effects of TCE. In particular, occupational exposure to TCE has been linked to less common conditions such as systemic sclerosis and pulmonary veno-occlusive disease.

Effects of a 5HT(2) receptor agonist on anaesthetized pigs susceptible to malignant hyperthermia

BACKGROUND

The pathophysiology of the serotoninergic system in malignant hyperthermia (MH) is not completely understood. The serotonin-2 (5HT(2A)) receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI) induces typical MH symptoms, including skeletal muscle rigidity, an increase in body temperature, hyperventilation and acidosis in conscious MH-susceptible (MHS) pigs. Whether these symptoms are directly generated in skeletal muscle, result from central serotonergic overstimulation or from a porcine stress syndrome remains unresolved. In this study the in vivo effects of DOI on anaesthetized (and thus stress-protected) MHS and MH-normal (MHN) pigs were investigated.

METHODS

and results. DOI 1 mg kg(-1) was administered three times at 40-min intervals to five MHS and five MHN anaesthetized pigs. Body temperature, heart rate, muscle tone, arterial carbon dioxide pressure (Pa(CO(2))), pH and creatine kinase concentrations were measured. The clinical occurrence of MH was defined by Pa(CO(2)) above 70 mm Hg and an increase in body temperature of more than 2 degrees C. Intragroup differences were analysed with the Friedman test as an overall non-parametric ANOVA and, in case of significance, with the Wilcoxon test. Intergroup comparisons were performed with the Mann-Whitney U-test (statistical significance P<0.05). MHS and MHN pigs developed muscle fasciculations, significant increases in body temperature and Pa(CO(2)) and a significant decrease in pH after the administration of DOI. These changes were comparable in both groups until the third dose of DOI, when in MHS pigs heart rate and Pa(CO(2)) rose significantly and pH fell significantly compared with MHN pigs. All MHS pigs fulfilled the MH criteria. Body temperature increased by more than 2 degrees C in all MHN pigs and Pa(CO(2)) exceeded 70 mm Hg in two. Thus, two MHN pigs fulfilled the criteria of MH.

CONCLUSIONS

The comparability of the clinical presentation following DOI administration in MHS and MHN animals and the order of the development of MH-like symptoms favour the hypothesis of a central serotonergic overstimulation, leading to a serotonin syndrome.

Pharmacodynamic effects of serotonin (5-HT) receptor ligands in pigs: stimulation of 5-HT2 receptors induces malignant hyperthermia

In pigs, the serotonin-2 (5-HT2) receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), 0.8 mg/kg, induced "psychotic" behaviour (e.g., grimacing, backward locomotion, blank stare) and a muscular syndrome, which is known as malignant hyperthermia (MH) in pigs and humans. This syndrome is characterized by generalized skeletal muscle rigidity, leading to an increase in body temperature, marked acidosis, hyperkaliaemia, cyanosis and elevation of lactate, carbon dioxide and the muscle enzyme creatine kinase (CK) in plasma. In pigs which were selectively bred for susceptibility to MH induction by known triggering agents, such as halothane, the administration of DOI was fatal in 3 out of 5 animals. In genetically susceptible pigs, MH was also induced by 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT), 0.5-1.8 mg/kg, and D-lysergic acid diethylamide (LSD), 60-110 micrograms/kg. Furthermore, 5-MeO-DMT and LSD induced head shakes in the animals, which had not been observed after DOI and could not be blocked by 5-HT2-antagonists, ketanserin (0.5-5 mg/kg) and ritanserin (1-2.5 mg/kg). The psychotomimetic effects of 5-MeO-DMT could be blocked by ketanserin or ritanserin, which, depending on the dose, also reduced or totally prevented the hyperthermia and metabolic changes induced by 5-MeO-DMT in pigs. Administration of 5-MeO-DMT, 1.8 mg/kg, was fatal in 4 of 5 MH-susceptible pigs, whereas pigs injected with this dosage after pretreatment with ketanserin (0.5-5 mg/kg) or ritanserin (1-2.5 mg/kg) did not die. In pigs from MH-resistant littermates, administration of 5-MeO-DMT was not fatal. Comparison of metabolic changes in susceptible and non-susceptible pigs suggested that the marked increase in plasma potassium, which arises principally from damaged muscle cells, is primarily responsible for the fatal effect of DOI and 5-MeO-DMT in genetically susceptible individuals. In MH-susceptible pigs, which were anesthetized, relaxed and artificially ventilated, 5-MeO-DMT did not induce hyperthermia, thus substantiating that the marked hyperthermia observed in conscious pigs was a result of muscle activation and not due to effects on thermoregulation or blood pressure. The results indicate that hallucinogenic drugs with 5-HT2 agonistic effects trigger a life-threatening syndrome, MH, in genetically susceptible pigs. 5-HT2 antagonists, such as ketanserin or ritanserin, are capable of counteracting the fatality of this syndrome.