Cytotoxicity related changes in biochemical cell function following in vitro cadmium treatment

Antagonism of cadmium cytotoxicity by differentiation inducers

Studies on the antagonism of toxicity can provide information about toxic mechanisms and suggest chemotherapeutic strategies. A rapid cell growth assay that measures the effects of test agents on the accumulation of cell protein (Shopsis and Eng, Toxicol. Lett. 1985;26:1) has been applied to studies of the antagonism of the cytotoxicity of cadmium. Exposure of Balb/c mouse 3T3 cells to 15 mumol/L Cd2+ for 24 h or 7 mumol/L Cd2+ for 48 h caused a 50% decrease in total cell protein. Zn2+ and selenite ion, antagonists of Cd toxicity in vivo, antagonized Cd2+ cytotoxicity when added in micromolar concentrations at the initiation of exposure to Cd2+. A diverse group of chemicals that can induce differentiation in vitro in cultured erythroleukemia and other cells were also found to antagonize the cytotoxic effects of Cd2+ to 3T3 cells. Dimethyl sulfoxide (DMSO), hexamethylene bisacetamide, N,N-dimethyl formamide, N-methyl formamide, dimethyl acetamide, hypoxanthine, hemin, ouabain, and sodium butyrate, when added to cultures simultaneously with Cd2+, each antagonized Cd2+ toxicity. These agents were used at concentrations equal to or lower than the concentrations at which they induce cellular differentiation. Other cytotoxicity assays and morphological studies confirmed these observations. DMSO added as much as 6 h after the initiation of a 24-h exposure to Cd2+ still protected cells; conversely, pretreatment of cultures with butyrate or DMSO for 24 h followed by their removal did not confer protection against subsequent Cd2+ challenge. Ethanol and methanol (noninducers of differentiation) did not antagonize Cd2+ cytotoxicity, and differentiation-inducing agents did not protect the cells from Zn(2+)- or Hg(2+)-induced cytotoxicity. DMSO treatment does not induce an increase in the concentrations of metallothionein or glutathione in these cells.

Placental transfer of metals of coal fly ash into various fetal organs of rat

Fly ash (100 mg/kg body weight) was administered intratracheally to 14-day pregnant rats for 6 consecutive days. On day 20 of gestation the translocation of metals present in the fly ash to various maternal and fetal organs was studied. Fly ash administration to pregnant mothers retarded the growth of fetal heart and kidney as determined by their weights. Fly ash instillation increased organ levels of nearly all the metals studied in both mother and fetus. Most of the metals present in coal fly ash were transferred in significant amounts through placenta to several fetal organs. However, the pattern of their distribution into various fetal organs was different for different metals.

Zinc amelioration of cadmium toxicity on preimplantation mouse zygotes in vitro

Zinc, at a concentration of 5 or 10 micrograms/ml medium, has been shown to protect mouse preembryos in vitro from the toxicity of cadmium at a concentration of 5 micrograms/ml medium after a simultaneous treatment of the ions from four-cell to morula or from morula to blastocyst for 24 hours. Such an amelioration indicates that cadmium toxicity is a result of the unique property of the cadmium ion and is not due to an alteration in the culture medium after the addition of an extra metallic ion. Zinc probably ameliorates cadmium-treated mouse preembryo by competing with cadmium for uptake or some other metabolic processes. In view of the well-documented competition between cadmium and zinc ions for binding sites in many other cell types, some macromolecules to which similar divalent metallic ions bind competitively may also exist in the mouse preembryo. This suggests that a protective mechanism dependent on the metal-metal interactions begins to operate in the mouse preembryo at a very early stage of differentiation before implantation.

Effects of cadmium on lactate dehydrogenase activities in mouse pre-embryos at various stages

A decline in LDH activity from four-cell to late blastocyst was demonstrated in pre-embryos from F1 (C57 female X A2G male) female mice. An exposure to 0.5 or 1 microgram/ml cadmium did not affect the in vitro development of the four-cell pre-embryos and morulae or their LDH activities. At 5 or 10 micrograms/ml cadmium, the in vitro development of the treated pre-embryos was affected. Although most of the treated four-cell pre-embryos had proceeded to compaction, they became degenerated 24 h after treatment. The LDH activity of these degenerated pre-embryos was higher than that in the control blastocysts. We propose that cadmium may interfere with the general energy metabolism of the cells. This causes a reduced rate of LDH degradation, leading to a slower decline in LDH activity in cadmium-treated pre-embryos. Failure of some critical biochemical processes after cadmium treatment may ultimately lead to the subsequent degeneration of the treated pre-embryos.

Triorganotin-induced cytotoxicity to rat thymus, bone marrow and red blood cells as determined by several in vitro assays

To further investigate the immunotoxic effects of tri-n-propyltin chloride (TPTC), tri-n-butyltin chloride (TBTC) and triphenyltin chloride (TPhTC) several cytotoxicity tests with a series of trialkyltin chlorides and TPhTC were carried out, using isolated rat thymocytes as target cells. Thymocytes, cultured in a serum-supplemented medium, were exposed to organotin concentrations ranging from 0.01 to 10 microM for periods up to 30 h. Parameters such as cell count, trypan blue exclusion, chromium release, thymidine incorporation and cyclic AMP production were used to evaluate the cytotoxicity of these compounds. The more lipophilic compounds TPTC, TBTC, tri-n-hexyltin chloride (THTC) and TPhTC appeared most cytotoxic, reducing thymidine incorporation at concentrations as low as 0.05-1 microM. Membrane damage as determined by trypan blue exclusion and chromium release occurred at higher levels (1-10 microM). The water soluble homologue trimethyltin chloride (TMTC) was least effective in all test models. When phosphate-buffered saline supplemented with glucose was used as incubation medium, TBTC appeared more cytotoxic to thymocytes. Using this medium in 5-h incubations the cytotoxicity of TBTC to thymus, bone marrow and red blood cells was compared. Bone marrow cells were slightly less sensitive than thymocytes, while red cells were relatively resistant. In conclusion, of the triorganotin compounds especially the lipophilic homologues are cytotoxic in vitro.