The effects of triethyltin bromide on red cell and brain cyclic AMP-dependent protein kinases

Effects of triphenyltin acetate on survival, hatching success, and liver ultrastructure of early life stages of zebrafish (Danio rerio)

In order to evaluate the toxicity of the fungicide triphenyltin acetate (TPTA) on hatching, survival, morphology, and histology of early life stages of zebrafish (Danio rerio), newly fertilized eggs were exposed to concentrations of 0.5, 5, 25, 75, and 100 microg/liter TPTA for 96 h at 28+/-0.5 degrees C. Embryos and larvae were kept under constant observation for up to 7 days and studied with respect to mortality and teratogenic effects as well as histological and cytological alterations in the liver as endpoints of sublethal toxicity of TPTA. Exposure to TPTA caused dose- and time-related effects with respect to all parameters investigated: (1) Hatching was delayed at concentrations >/=0.5 microg/liter TPTA; (2) mortality increased at >/=25 microg/liter TA after 96 h exposure, with TPTA toxicity being higher in larval than in embryonic stages; (3) from >/=25 microg/liter, larvae exhibited skeletal malformation, retarded yolk sac resorption, and edema in the heart and yolk sac regions; and (4) histo- and cytopathological alterations of larval liver included changes in nuclei and mitochondria as well as glycogen depletion from >/=0.5 microg/liter TPTA. The study thus demonstrates not only an elevated sensitivity of zebrafish embryos to TPTA in stages prior to hatching, but also the importance of continuous observation over extended periods after termination of the actual exposure for a comprehensive evaluation of the toxicity of chemical compounds.

Toxicity of dibutyltin, tributyltin and other organotin compounds to humans and to experimental animals

Alkyltin compounds are used as stabilizers and antifouling agents. Food chain accumulation and bioconcentration have been demonstrated in crabs, oysters and salmon exposed to tributyltin oxide. In mammalian species, tributyltin compounds may be metabolized to dibutyltin derivatives and related metabolites. Di- and tributyltins appear to be less potent neurotoxicants than trimethyltins and triethyltins. Dibutyltins and tributyltins produced bile duct damage in rats, mice and hamsters. Tributyltin oxide and dibutyltin and dioctyltin compounds are potent thymolytic and immunotoxic agents in rats. Tributyltin oxide at 5 ppm in the rat diet produced immunotoxicity in a 2-year feeding study, and at 50 ppm increased the incidence of tumors of endocrine origin. In preliminary reports, 5 ppm tributyltin produced no detectable increase in tumor incidence, and 0.5 ppm produced no detectable immunotoxicity in long-term studies. Tributyltin oxide and dibutyltin acetate did not appear to be mutagenic in a large battery of mutagenicity assays but produced base-pair substitutions in one of the bacterial strains tested. Tributyltin oxide produced mutations in Chinese hamster ovary cells, increased the incidence of micronuclei in the erythrocytes of exposed male BALB/c mice, and was highly embryotoxic in vitro. Embryotoxic and teratogenic effects in mice exposed to tributyltin oxide in vivo may have been due either to direct tributyltin oxide action or responses secondary to maternal toxicity. More information is needed to determine the applicability to human risk assessments of the immunotoxicity data derived from rat studies and to establish a definitive tolerable daily intake for tributyltin oxide.

Inhibition of oxidative phosphorylation by organotin thiocarbamates

A series of triphenyl-, tricyclohexyl- and tribenzyltin compounds have been synthesized and examined as inhibitors of mitochondrial oxidative phosphorylation. All compounds tested inhibit oxidative phosphorylation linked to succinate oxidation by potato tuber mitochondria. All of the organotin compounds inhibit ADP-stimulated O2 uptake linked to succinate oxidation with concentrations for 50% inhibition in the range 2-50 microM. This inhibition is not due to inhibition of electron transport from succinate to O2 per se: none of the organotin compounds at 50 microM substantially inhibit the rate of succinate oxidation in the presence of 2,4-dinitrophenol. Representative organotin compounds at 0.5-50 microM do not act as uncouplers of succinate oxidation. It is concluded that the organotin compounds act as energy transfer inhibitors to inhibit oxidative phosphorylation in potato tuber mitochondria. A similar mode of action of representative organotin compounds was found with rat liver mitochondria. These organotin compounds inhibit a hydrophobic Ca2+-dependent plant protein kinase in the absence but not in the presence of thiols.

The effects of trimethyltin on the Ca+2, Mg+2 and Ca+2 + Mg+2-dependent ATPases of human neuroblastoma GM 3320

Data presented here indicate neuroblastoma GM 3320 tissue homogenates exhibit ouabain insensitive Ca+2-dependent, Mg+2-independent, Mg+2-dependent, Ca+2-independent and Ca+2 + Mg+2-dependent ATPase activities. Inclusion of trimethyltin in homogenate preparations of these cells appears to discriminate between these various ATPase activities. At low concentrations (25 microM), trimethyltin preferentially stimulated the Ca+2-dependent, Mg+2-independent ATPase activity while inhibiting the Ca+2 + Mg+2-ATPase activity approximately 70%. At 75 microM trimethyltin, the Ca+2 + Mg+2-dependent ATPase activity is inhibited greater than 95% while the Ca+2-dependent, Mg+2-independent activity is essentially unchanged from control activity and the Mg+2-dependent, Ca+2-independent activity is inhibited approximately 50%. At concentrations greater than 75 microM, trimethyltin significantly inhibits the Ca+2-dependent, Mg+2-independent ATPase activity. Thus, at trimethyltin concentrations of 50-75 microM, preferential inhibition of the Mg+2-dependent, Ca+2-independent and Ca+2 + Mg+2-dependent ATPase activities of neuroblastoma GM 3320 is achieved.

Effects of triethyltin bromide on protein phosphorylation in subcellular fractions from rat and rabbit brain

Phosphorylation of specific proteins in subcellular fractions of rat brain is affected by the presence of low concentrations (1-50 microM) of triethyltin bromide (Et3SnBr), in vitro. SDS-PAGE and autoradiography showed that Et3SnBr increased phosphorylation of an Mr = 42,000 phosphorylation of an Mr = 52,000 component. The Mr = 42,000 and 76,000-80,000 phosphoproteins have been identified as the alpha-subunit of pyruvate dehydrogenase (PDH) and synapsin, respectively. Et3SnBr-induced phosphorylation of rabbit brain PDH results in partial inactivation of the PDH complex.

Structural model for the trialkyltin binding site on cat hemoglobin

The binding site for trialkyltin complexes on the alpha- chain of cat oxyhemoglobins is proposed to involve the SG and NE2 atoms of Cys-13 and His-113 respectively. On deoxygenation, the conformation of this region changes substantially, allowing complexation only through the ND1 nitrogen atom of His-113, a much less favorable interaction. Thus the model presented explains the preferential binding of trialkyltin complexes to R-state cat hemoglobin and suggests the type of interaction that is likely to occur between these compounds and a variety of less well-characterized enzymes to produce the metabolic effects that trialkyltin complexes are known to produce in vivo.

Decreased adenosine cyclic 3',5'-monophosphate phosphodiesterase activity in rat brain following triethyltin intoxication

The possible involvement of cerebral cAMP-phosphodiesterase (PDE) in the intoxication and brain edema formation after exposure to triethyltin (TET) has been studied in vitro and in vivo in the rat. In vitro studies showed an irreversible inhibition of the particulate and soluble phosphodiesterase activities. In vivo, both high i.v. single dose and repeated oral administration of low TET doses led to a significant decrease of the particulate activities. Phosphodiesterase inhibition preceded edema formation. The soluble activities were less influenced and their inhibition could be a consequence of the edema formed in the brain tissue rather than of a TET direct action upon the enzyme. Kinetic analysis of the brain particulate enzyme from the TET-treated rats showed a significant decrease in the Vmax of the substrate high affinity enzyme form when compared to controls.