Prediction of Human Lethal Doses and Concentrations of MEIC Chemicals from Rodent LD50 Values: An Attempt to Make Some Reparation

The prediction of human toxicities from animal toxicity tests is often poor, and is now discouraged and in some cases banned, especially those involving the LD₅₀ test. However, there is a vast number of historical LD₅₀ data in both public and in-house repositories that are being put to little use. This study examined the correlations between human lethality (doses and concentrations) of 36 MEIC chemicals and the median values of a large number of mouse and rat LD₅₀ values obtained for four different routes of administration. The best correlations were found with mouse and rat intraperitoneal LD₅₀ values (r² = 0.838 and 0.810 for human lethal dose, and r² = 0.753 and 0.785 for human lethal concentration). The results show that excellent prediction of human lethal dose and concentration can be made, for this series of chemicals at least, by using uncurated rodent LD₅₀ values, thus offering some reparation for the millions of rodent lives sacrificed in LD₅₀ testing.

Preliminary in vitro cytotoxicity screening of a bead-formed macroporous hydrophilic polymer matrix

A prescreen of the in vitro cytotoxicity of both the primary fabrication components and potential leachables from a bead-formed macroporous poly(2-hydroxyethyl methacrylate), (pHEMA) matrix has been carried out using INVITTOX Neutral red and Kenacid blue R dye binding methods. Of the eluants obtained from 24, 48, and 72-h incubated beads, only the 72-h eluant produced a greater than 20% (ID20) inhibition of 3T3-L1 cell proliferation with values of 20.98 +/- 2.33% and 21.41 +/- 1.37% inhibition for the Neutral red and Kenacid blue R binding methods, respectively. ID50 values for the fabrication components obtained using the Kenacid blue R method were generally higher than those obtained by the Neutral red assay, although the ranking of the chemicals in terms of their relative cytotoxicities was identical by both methods, i.e. ethylene glycol dimethacrylate > uranyl nitrate > purified HEMA > n-hexane > ethylene glycol (mmol 1(-1)). Whilst extended washing of finished PHEMA beads in water will reduce their acute in vitro cytotoxicity, this will only be achieved with some loss of previously encapsulated water soluble macromolecules.

The cytotoxicity of 50 chemicals from the MEIC study determined by growth inhibition of ascites sarcoma BP8 cells: a comparison with acute toxicity data in man and rodents

In this study, 50 chemicals selected on the basis of existence of particularly reliable human toxicity data were screened in a cytotoxicity test involving inhibition of the growth of Ascites Sarcoma BP8 cells. These test results are part of an international validation program, the Multicenter Evaluation of In Vitro Cytotoxicity (MEIC), the aim of which is to recommend batteries of in vitro tests to be used for prediction of human toxicity. The cytotoxicities (expressed as the concentrations causing 50% inhibition of cell growth) were compared to acute toxicity data in humans (LDL0) and rodents (LD50), showing the best correlation to rodent data. The results are discussed in relationship to what is usually referred to as basal cytotoxic mechanisms as a cause of in vivo toxicity. It could be concluded that the predicted results on the basis of mechanistic reasoning were not always obtained.