Disposition of 14C and/or 74As-cacodylic acid in rats after intravenous, intratracheal, or peroral administration.

The distribution, excretion, and possible metabolism of (14)C- and/or (74)As-cacodylic acid, an organoarsenical herbicide, was studied in rats following a single intravenous injection, intratracheal instillation or oral gavage. Male Sherman rats were dosed at levels ranging from 200 mg/kg to 120 mug/kg. The extent and rate of lung absorption was greater than gastrointestinal absorption. Concentrations in the liver and whole blood were higher after peroral dosing than intravenous administration. Levels observed in plasma and other tissues were similar after all three routes following the absorptive phase. The percent dose found in the whole blood, red blood cells, and plasma was similar for all doses given by these routes. Less than 0.1(1/2) of the administered dose was recovered as (14)CO(2) by any route at 24 hr after administration. Twenty-four hours after intravenous, intratracheal, and peroral administration, 71, 60, and 25%, respectively, was excreted in the urine. After intravenous administration of 200 mg/kg, sufficient (14)C-cacodylic acid was recovered in bile to account for the small amount excreted in the feces. Cacodylic acid is probably not metabolized to inorganic arsenic since the disposition of (14)C and (74)As-cacodylic acid were identical.Kinetic analyses of the plasma curve for (14)C-cacodylic acid (high dose) yielded three half-times; 0.014, 0.214 and 3.42 hr with an apparent volume of distribution of 15.3 ml. Highest initial concentrations were found in the whole blood, muscle, kidney, liver and lung. Levels in all tissues decreased rapidly, but remained high in whole blood. The red blood cells were found to be the major site of body burden of cacodylic acid.

The CTFA Evaluation of Alternatives Program: an evaluation of in vitro alternatives to the Draize primary eye irritation test. (Phase II) oil/water emulsions.

The Cosmetic, Toiletry and Fragrance Association (CTFA) Evaluation of Alternatives Program is an evaluation of the relationship between Draize ocular safety test data and comparable data from a selection of in vitro tests. In Phase II, 18 representative oil/water-based personal-care formulations were subjected to the Draize primary eye safety test and 30 in vitro assay protocols (14 different types of in vitro endpoints were evaluated; the remainder were protocol variations). Correlation of in vitro with in vivo data was evaluated using analysis of sensitivity/specificity and statistical analysis of the relationship between maximum average Draize score (MAS) and in vitro endpoint. Regression modelling is the primary approach adopted in the CTFA Program for evaluating in vitro assay performance. The objective of regression analysis is to predict MAS for a given test material (and to place upper and lower prediction interval bounds on the range in which the MAS is anticipated to fall with high probability) conditional on observing an in vitro assay score for that material. The degree of confidence in prediction is quantified in terms of the relative widths of prediction intervals constructed about the fitted regression curves: the narrower the prediction interval, the more predictive of the Draize score is the in vitro test result. 16 assays were shown to have the greatest agreement with the Draize procedure and were therefore selected for regression analysis. Based on the magnitude of the 95% prediction bounds of each of the 16 selected assays over the range of test data, it may be inferred that prediction of MAS values from experimentally determined in vitro scores is more accurate for oil/water-based formulations with lower rather than higher irritancy potential. The assays selected for modelling in Phase II generally exhibited weaker relationships with MAS than those selected in Phase I (evaluated using hydroalcoholic formulations), even though several assays were common to both Phases.

The CTFA Evaluation of Alternatives Program: an evaluation of in vitro alternatives to the Draize primary eye irritation test. (Phase III) surfactant-based formulations.

The CTFA Evaluation of Alternatives Program is an evaluation of the relationship between data from the Draize primary eye irritation test and comparable data from a selection of promising in vitro eye irritation tests. In Phase III, data from the Draize test and 41 in vitro endpoints on 25 representative surfactant-based personal care formulations were compared. As in Phase I and Phase II, regression modelling of the relationship between maximum average Draize score (MAS) and in vitro endpoint was the primary approach adopted for evaluating in vitro assay performance. The degree of confidence in prediction of MAS for a given in vitro endpoint is quantified in terms of the relative widths of prediction intervals constructed about the fitted regression curve. Prediction intervals reflect not only the error attributed to the model but also the material-specific components of variation in both the Draize and the in vitro assays. Among the in vitro assays selected for regression modeling in Phase III, the relationship between MAS and in vitro score was relatively well defined. The prediction bounds on MAS were most narrow for materials at the lower or upper end of the effective irritation range (MAS = 0-45), where variability in MAS was smallest. This, the confidence with which the MAS of surfactant-based formulations is predicted is greatest when MAS approaches zero or when MAS approaches 45 (no comment is made on prediction of MAS > 45 since extrapolation beyond the range of observed data is not possible). No single in vitro endpoint was found to exhibit relative superiority with regard to prediction of MAS. Variability associated with Draize test outcome (e.g. in MAS values) must be considered in any future comparisons of in vivo and in vitro test results if the purpose is to predict in vivo response using in vitro data.

A Comparison of Three Cytotoxicity Endpoints in the Corneal HCE-T Model.

The prediction of ocular irritation potential from in vitro assays still presents a problem, despite a number of validation trials. A study with coded cosmetic formulations, for which historic in vivo data were available, has been conducted with a human corneal multi-layered model system. This corneal model, the HCE-T model, was developed by using HCE-T cells, a transfected human corneal epithelial cell line. The relative effectiveness of three endpoints that provide a measure of cytotoxicity in the HCE-T model was evaluated. Cell viability immediately after exposure to the test materials was determined by using the MTT and Alamar Blue™ (AB) assays, and, 24 hours later, by using the MTT, AB and lactate assays. Viability measurements with the MTT, AB and lactate assays gave similar dose-response curves at the 24-hour endpoint. One formulation (an anti-dandruff shampoo) caused a less severe drop in viability in assays conducted immediately after the exposure than at the 24-hour time-point. There was little deterioration in viability with the other test materials. The ranking of the test formulations on the basis of relative loss of viability and release of lactate resulted in the same order as for the Modified Maximum Average Draize Test Score. Comparison of the HCE-T model cytotoxicity assay results with historic in vitro data from two different cytotoxicity assays, conducted by using fibroblast monolayer cultures and the same materials, indicated that the multi-layered corneal model had a greater predictive ability. The results of a blind trial with the lactate assay in two laboratories indicated that the techniques required were transferable between laboratories. The lactate results were reproducible between laboratories, even when cultures derived from different passage human corneal cells were tested, provided that the passage number was below 20.

The sensitization potential of D & C Yellow No. 11 in guinea pigs.

The certified drug and cosmetic dye substance known as D & C Yellow No. 11 [2-(2-quinolyl)-1,3 indandione] was tested for its dermal sensitization potential in guinea pigs. An induction regimen consisting of a single footpad injection of Complete Freund's Adjuvant diluted with antigen, and an intradermal injection of antigen, produced delayed-type hypersensitivity reactions. A high sensitization frequency was observed with 50 micrograms D & C Yellow No. 11 and the positive control 2,4-dinitrochlorobenzene (DNCB). The reaction severities of both DNCB and 50 micrograms D & C Yellow No. 11 were comparable. A dose-response profile was obtained with D & C Yellow No. 11 employing several concentrations (50, 250 and 500 micrograms/ml). Histologic examination of selected skin sites demonstrated a cellular inflammatory response which was consistent with delayed-type hypersensitivity.

Evaluation of a human corneal epithelial cell line as an in vitro model for assessing ocular irritation.

A human corneal epithelial cell line, 10.014 pRSV-T (HCR-T cells), has been used to develop a three-dimensional in vitro model of the human corneal epithelium (HCE-T model). HCE-T cells form a stratified culture when grown at the air-liquid interface on a collagen membrane in serum-free medium. This model served as the basis for assays which supported the ocular irritancy assessment of water-soluble test substances. Cellular alterations in the HCE-T model were measured following 5-min topical exposures to 20 chemicals [listed in the European Center for Ecotoxicology and Toxicology of Chemicals (ECETOC) Reference Chemicals Data Bank] and 25 surfactant-based product formulations [utilized in the Cosmetic, Toiletry, and Fragrance Association (CTFA) Alternatives Program Phase III]. In vitro assays used were transepithelial permeability to sodium fluorescein (TEP) and transepithelial electrical resistance (TER). These measured alterations in the barrier function of this corneal epithelial equivalent. Barrier function is a well-developed property in the HCE-T model that supports the mechanistic relevance of these assays. In vitro data, averaged from replicate assays, were compared to respective Draize rabbit eye irritation data from the publicly available ECETOC and CTFA databases using linear regression with Pearson's correlation analysis. For chemicals, Pearson's correlation coefficients, r, from comparisons of Draize maximum average scores (MAS) to TEP and TER data were 0.71 and 0.55, respectively. For product formulations, Pearson's correlation coefficients from comparisons of Draize MAS to TEP and TER data were 0.86 and 0.80, respectively. Data indicated that barrier function alterations in the HCE-T model correlated with ocular irritancy and corneal toxicity. While the irritancy of the chemicals tested was effectively assessed only by the TEP assay, that for the surfactant-based product formulations was effectively assessed by both the TEP and TER assays. Results also suggested that the HCE-T TEP and TER assays vary in their effectiveness for evaluating specific classes of test materials.