Bovine bladder urothelial cell activation of carcinogens to metabolites mutagenic to Chinese hamster V79 cells and Salmonella typhimurium.

The ability of bovine bladder urothelial cells to activate genotoxic chemicals to mutagens was examined by cocultivating bladder cells with Chinese hamster V79 cells or Salmonella typhimurium as mutable targets. Activation of test chemicals to mutagenic intermediates by urothelial cells was detected by induction of 6-thioguanine resistance in V79 cells or by induction of histidine revertants in Salmonella. In the bladder cell-mediated V79 cell mutagenesis system, a significant increase in mutation frequency was induced by exposure to 7,12-dimethylbenz(a)anthracene and dimethylnitrosamine. The aromatic amines 2-aminofluorene, 2-acetylaminofluorene, and 4-aminobiphenyl were weakly mutagenic to V79 cells with bladder cell activation, while no mutagenic activity was detected with 1-naphthylamine, 2-naphthylamine, or benzidine. Because the mutagenic activity of the aromatic amines was low with V79 cells as the target, a bladder cell-mediated S. typhimurium system was developed for these chemicals. The aromatic amines 2-aminofluorene, 2-acetylaminofluorene, 4-aminobiphenyl and 2-naphthylamine were mutagenic to S. typhimurium TA98 and TA100 in the presence of bladder cells but not in their absence. Benzidine was mutagenic to TA98 but not to TA100. The putative noncarcinogen 1-naphthylamine was not mutagenic in the system. In contrast to the V79 data, 7,12-dimethylbenz(a)anthracene and dimethylnitrosamine were not mutagenic with either bacterial strain. Mutagenic responses were related to both the number of bladder cells used for activation and the concentration of test chemical in the Salmonella assay. The data demonstrate that bovine bladder urothelial cells can activate carcinogens from three chemical classes to mutagens and indicate the different sensitivities of V79 cells and S. typhimurium to genotoxic agents.

Relationship of N-arylacetamide metabolism and macromolecular binding to oncogenic transformation of C3H10T1/2CL8 cells.

The C3H10T1/2CL8 mouse embryo oncogenic transformation bioassay system detects a wide variety of chemical carcinogens. However, one carcinogen that does not transform C3H10T1/2CL8 cells is the liver carcinogen N-2-fluorenylacetamide (FAA). Previous reports indicate that an activated form of FAA, N-acetoxy-FAA (N-OAc-FAA), transforms these fibroblasts. In an effort to understand these results, the metabolism and binding to cellular macromolecules of FAA and N-OAc-FAA using C3H10T1/2CL8 cells was investigated. C3H10T1/2CL8 cells metabolized FAA to 7-hydroxy-FAA, 2-fluorenylamine and N-hydroxy-FAA (N-OH-FAA) at rates of 5.03, 2.22 and 3.33 pmol/h/10(6) cells, respectively. N-O-Ac-FAA was bound to the DNA and RNA in C3H10T1/2CL8 cells to the extent of 10.6 and 3.6 FAA residues/10(6) nucleotides, respectively, and to protein at 21.9 pmol FAA residues/mg protein. However, binding of FAA to DNA and RNA at similar concentrations to N-OAc-FAA was less than 0.3 and 0.6 residues/10(6) nucleotides, respectively. These results strongly indicate that the inability of FAA to transform C3H10T1/2CL8 cells residues in the cells' inability to metabolize it sufficiently to the proximate carcinogen N-OH-FAA and not an inherent insensitivity to its activated forms.

Activation of aromatic amines to mutagens by bovine bladder and liver cells.

A bovine bladder cell-mediated mutagenesis system using Chinese hamster V79 cells and Salmonella typhimurium as target organisms was developed to investigate the capacity of the bladder urothelium to activate chemical carcinogens. Bovine bladder epithelial cells can activate the aromatic amines AF and 4-ABP to intermediates which mutate V79 cells and S. typhimurium TA 98 and TA 100. DMBA was mutagenic to V79 cells but not detectably mutagenic to either Salmonella strain with bladder cell activation. The chemicals tested were not mutagenic to either target organism in the absence of bladder cells. In contrast to the response with DMBA, S. typhimurium was a more sensitive target for the arylamines than V79 cells. These data suggest the value of using multiple end points for assessing metabolic capability. The activation capability of intact bladder cells was compared to disrupted cells, and S-9 prepared from bladder cells used with and without cofactors. When intact cells or S-9 plus cofactors were used as the activation system a dose-dependent increase in revertants was observed for 4-ABP. A bovine liver cell-mediated bacterial mutagenesis system was also developed and the liver and bladder systems compared. For AF, bladder cells appear to be at least ten times more active per viable cell than hepatocytes in producing mutagenic intermediates, while 4-ABP is essentially not mutagenic in the hepatocyte-mediated system. A quantitative comparison of the relative importance of the liver and bladder to activate the chemicals is difficult to make but the data indicate the ability of the bladder epithelium to activate bladder carcinogens.

Cell-mediated mutagenesis of Chinese hamster V79 cells and Salmonella typhimurium.

In the cell-mediated approach, intact cells metabolically activate the chemical and the genetic end points are measured in cocultivated or coincubated target cells. Cell-mediated systems have been used to study fundamental problems in carcinogenesis, such as organ and species specificity of carcinogen activation, and in screening for carcinogenic chemicals. In the studies discussed here, cells from various rat, hamster, or bovine tissues are used to metabolically activate the chemical, and mutation and/or SCE induction in V79 cells and mutation of S. typhimurium are measured as genetic end points. The detection of genetic activity of a chemical depends both on the cell (organ, species, type, etc.) used for metabolic activation and on the genetic end point measured. Hydrocarbons and nitrosamines are two classes of environmentally significant chemicals that are sensitively detected with cell-mediated systems. The cell-mediated approach provides a valuable metabolic activation component for short-term in vitro systems, and further studies are needed to utilize and evaluate its full potential.

In vitro murine embryotoxicity of cyclophosphamide in embryos co-cultured with maternal hepatocytes: development and application of a murine embryo-hepatocyte co-culture model.

The technique of whole embryo culture provides a sensitive model to evaluate both the effects, and their underlying mechanisms, of drugs and environmental chemicals on embryonic development, independent of maternal influences. However, before teratogenic expression, many teratogens must be enzymatically bioactivated to toxic reactive intermediates. To detect such proteratogens, the embryo culture model may need to be coupled with an exogenous bioactivating system if maternal and/or placental metabolism is involved. We developed a similar embryo-hepatocyte co-culture system using embryos and maternal hepatocytes from mice, which often are more sensitive than rats to chemical teratogens, and which may have a balance of phase II drug metabolising enzymes more similar to humans. This murine system was then used to evaluate the relative maternal and embryonic contributions to cyclophosphamide embryopathy. Day 9.5 (morning of plug = day 1) murine embryos were co-cultured for 24 h in vitro with primary cultures of murine maternal hepatocytes (> 85% viability). Murine embryos were exposed to cyclophosphamide concentrations (0, 7.5, 15, 25 micrograms/ml), similar to those used in rat embryo culture studies. Murine embryos co-cultured with murine maternal hepatocytes developed normally, as did embryos exposed to cyclophosphamide in the absence of hepatocytes. Maternal hepatocytes were necessary for the expression of cyclophosphamide embryotoxicity, which was concentration-dependent, as demonstrated by increasing severity of reductions in crown rump length, yolk sac diameter and somite number. These results show that the co-culture of murine maternal hepatocytes and embryos is feasible, and suggest that maternal bioactivation is required for murine cyclophosphamide embryopathy.

In vitro culture of postimplantation hamster embryos.

In vitro culture of intact rat and mouse embryos has been described extensively, but information on the culture of other species is sparse. The present study examined some culture requirements of early somite stage hamster embryos and assessed the embryotoxic effects of sodium salicylate (SS), a direct acting chemical and cyclophosphamide (CP), a proteratogen, on these embryos. Hamster embryos explanted on gestation days (GD) 8 and 9 were cultured in Waymouth's embryo-hepatocyte co-cultivation medium (WEHC), 70% McCoy's 5A medium-30% male rat serum (MMRS) or 100% male rat serum (MRS) for 24 hours under various oxygen concentrations. Embryos cultured GD 8 to 9 in the various media grew and differentiated much as they did in vivo, while embryos cultured GD 9 to 10 grew best in MMRS as compared to embryos at the same stage in vivo. Embryos exposed to SS in MMRS at concentrations of 250, 300, or 400 micrograms/ml showed dose related embryotoxicity which included CNS defects, absence of hind limb bud formation, and lack of axial rotation. Hamster embryos co-cultivated with pregnant hamster hepatocytes and treated with 2.5, 6.25 and 12.5 micrograms/ml of CP, showed dose-dependent toxicity when compared to co-cultivated controls. Hamster embryos develop extensively in culture over a 24 hour period. This system may therefore provide a valuable tool for evaluating the species differences of a variety of potential teratogens and embryotoxins and allow the comparison of these embryotoxic effects between rat, mouse and hamster during similar stages of organogenesis.

In vivo and in vitro structure-dosimetry-activity relationships of substituted phenols in developmental toxicity assays.

Structure-dosimetry-activity relationships (SDARs) of a series of substituted phenols were evaluated following exposure of gestation day 11 rats in vivo and in comparable stage embryos in vitro. In the in vivo study, 27 congeners were assayed and log P (a term used synomously with lipophilicity in this paper) and Hammett sigma values (a measure of the electronic withdrawing ability of the substituent) were shown to correlate with maternal toxicity; however, no relationships between these parameters and developmental effects were observed. In the in vitro system, 13 congeners were evaluated and molar refractivity and/or lipophilicity were shown to correlate with the ability of the phenols to induce embryonic growth retardation and structural defects in the absence of the hepatocytes. In contrast, when a metabolic activating system (primary hepatocytes) was present in the in vitro system, the potential to induce growth retardation was inversely related to lipophilicity, although the relationships were weaker than the positive relationship seen without the hepatocytes. The binding of the phenols to macromolecules in the culture medium was highly correlated with log P. Correcting the in vitro potency data for the variable amount of binding improved the predictiveness of the quantitative structure-activity relationships (QSARs). The potential to induce embryotoxicity in vitro was not well correlated with the potential to induce developmental toxicity in vivo: whereas the in vitro data demonstrates that the phenols are intrinsically embryotoxic, few of them actually produced significant developmental toxicity in the in vivo system, and there were few positive correlations between effects observed in the two systems.(ABSTRACT TRUNCATED AT 250 WORDS)

Induced hepatocytes as a metabolic activation system for the mouse-lymphoma assay.

We have developed methods for the coculture of hepatocytes and mouse lymphoma cells and have shown that this system can be used for evaluating promutagens from several chemical classes (Brock et al., 1987). In the present study we investigated the use of hepatocytes isolated from rats pretreated with a cytochrome P-450 inducer (PB) or a P-448 inducer (BNF). CP-induced mutagenicity was higher in the presence of PB-induced hepatocytes than in control hepatocytes. Control and BNF-induced hepatocytes were evaluated with B(a)P, B(l)A, and BA. A dose-related positive response was observed with B(a)P and B(l)A both in the presence of control or induced hepatocytes; however, somewhat higher mutant frequencies were obtained in the presence of BNF-induced hepatocytes. BA induced a very weak positive response (approx. 2 X b.g.) in the presence of control hepatocytes and was weakly positive in the presence of BNF-induced hepatocytes. Benzene was tested using control and both PB- and BNF-induced hepatocytes. Neither of these approaches were successful in activating benzene to a mutagenic metabolite. These studies indicate that for some chemicals the mutagenic response of mouse lymphoma cells can be increased by inducing hepatocytes prior to isolation and cocultivation, and expands the use of hepatocytes for research evaluating chemicals requiring metabolic activation.

Population sampling in European air pollution exposure study, EXPOLIS: comparisons between the cities and representativeness of the samples.

A personal air pollution exposure study, EXPOLIS, was accomplished in six European cities among 25- to 55-year-old citizens. In order to compare the exposure results and different microenvironmental concentrations between the cities it is crucial to know the extent and effects of the population bias that has developed in sampling procedure and the sociodemographic characteristics of each measured population sample. In each participating city a random Base sample of 2000 to 3000 individuals was drawn from the census and a Short Questionnaire (SQ) was mailed to them. Two subsamples of the Respondents of the mailed questionnaire were randomly drawn: Diary sample for 48-h time--microenvironment--activity diary and extensive exposure questionnaires, and Exposure sample for the same plus personal exposure and microenvironmental monitoring. Significant differences existed between the EXPOLIS cities in the population-sampling procedure. Population-sampling bias was evaluated by comparing the Respondents with the total city populations. The share of women and individuals with more than 14 years of education is higher among the Respondents than the overall population except in Athens. Men, younger (25-34 years old) and unmarried individuals were hardest to get to participate in the study at least in Helsinki. The two subsamples differ from Respondents in having more employed and higher- educated individuals. The largest sample bias occurred at the first and easiest step of responding to the mailed Short Screening Questionnaire, and not at the last and most demanding stage of participating in the exposure measurements. Exposure data from some of EXPOLIS cities can only be compared to other cities with caution considering their large population bias or different sample selections. However the selection bias is not necessarily a problem for analyses about predictors of personal exposures or analyses within a city.

Personal exposure assessment studies may suffer from exposure-relevant selection bias.

We evaluated exposure-relevant selection bias within the framework of a study on personal air pollution exposure, using traffic data as exposure proxy. Based on random samples of 3000 (Basel) and 2532 (Helsinki) persons, 50 and 250 subjects, respectively, were recruited for direct monitoring and 250 (Basel, Helsinki) for indirect monitoring. In Basel, participants of direct monitoring as compared to non-participants were more likely to live at streets with low traffic volume (49% below 1st quartile vs. 27%). Adjusted for sex, age and nationality, an increase of 100 cars per hour was associated with 14% less participation (odds ratio (OR): 0.861; 95% CI: 0.731, 1.007). Although in Helsinki, traffic volume was neither significantly related to participation in direct nor indirect monitoring, the point estimates indicate a tendency to decreased participation with increasing traffic intensity at home. We conclude that selection bias regarding exposure-relevant characteristics is likely to occur when recruiting participants for studies including demanding personal exposure assessment. Correction for factors routinely collected may not fully account for exposure-relevant bias. This is of particular importance when using exposure data for modelling population exposure distributions, whereas in epidemiological studies, a reduced range of exposure must not a priori distort the exposure-response relationship.

Fine particle (PM25) measurement methodology, quality assurance procedures, and pilot results of the EXPOLIS study.

EXPOLIS is a European multicenter (Athens, Basel, Grenoble, Helsinki, Milan, and Prague) air pollution exposure study. It is the first international, population-based, large-scale study, where personal exposures to PM2.5 aerosol particles (together with volatile organic compounds and carbon monoxide) are being monitored. EXPOLIS is performed in six different centers across Europe, the sampled aerosol concentrations vary greatly, and the microenvironmental samples are not collected with the same equipment as the personal samples. Therefore careful equipment selection, methods development and testing, and thorough quality assurance and quality control (QA & QC) procedures are essential for producing reliable and comparable PM2.5 data. This paper introduces the equipment, the laboratory test results, the pilot results, the standard operating procedures, and the QA & QC procedures of EXPOLIS. Test results show good comparability and repeatability between personal and microenvironmental monitors for PM2.5 at different concentration levels measured across Europe in EXPOLIS centers.

Spatial variability of different fractions of particulate matter within an urban environment and between urban and rural sites.

The spatial variability of different fractions of particulate matter (PM) was investigated in the city of Basel, Switzerland, based on measurements performed throughout 1997 with a mobile monitoring station at six sites and permanently recorded measurements from a fixed site. Additionally, PM10 measurements from the following year, which were concurrently recorded at two urban and two rural sites, were compared. Generally, the spatial variability of PM4, PM10, and total suspended particulates (TSP) within this Swiss urban environment (area = 36 km2) was rather limited. With the exception of one site in a street canyon next to a traffic light, traffic density had only a weak tendency to increase the levels of PM. Mean PM10 concentration at six sites with different traffic densities was in the range of less than +/- 10% of the mean urban PM10 level. However, comparing the mean PM levels on workdays to that on weekends indicated that the impact of human activities, including traffic, on ambient PM levels may be considerable. Differences in the daily PM10 concentrations between urban and more elevated rural sites were strongly influenced by the stability of the atmosphere. In summer, when no persistent surface inversions exist, differences between urban and rural sites were rather small. It can therefore be concluded that spatial variability of annual mean PM concentration between urban and rural sites in the Basel area may more likely be caused by varying altitude than by distance to the city center.

Validity of ambient levels of fine particles as surrogate for personal exposure to outdoor air pollution--results of the European EXPOLIS-EAS Study (Swiss Center Basel).

To evaluate the validity of fixed-site fine particle levels as exposure surrogates in air pollution epidemiology, we considered four indicator groups: (1) PM2.5 total mass concentrations, (2) sulfur and potassium for regional air pollution, (3) lead and bromine for traffic-related particles, and (4) calcium for crustal particles. Using data from the European EXPOLIS (Air Pollution Exposure Distribution within Adult Urban Populations in Europe) study, we assessed the associations between 48-hr personal exposures and home outdoor levels of the indicators. Furthermore, within-city variability of fine particle levels was evaluated. Personal exposures to PM2.5 mass were not correlated to corresponding home outdoor levels (n = 44, rSpearman (Sp) = 0.07). In the group reporting neither relevant indoor sources nor relevant activities, personal exposures and home outdoor levels of sulfur were highly correlated (n = 40, rSp = 0.85). In contrast, the associations were weaker for traffic (Pb: n = 44, rSp = 0.53; Br: n = 44, rSp = 0.21) and crustal (Ca: n = 44, rSp = 0.12) indicators. This contrast is consistent with spatially homogeneous regional pollution and higher spatial variability of traffic and crustal indicators observed in Basel, Switzerland. We conclude that for regional air pollution, fixed-site fine particle levels are valid exposure surrogates. For source-specific exposures, however, fixed-site data are probably not the optimal measure. Still, in air pollution epidemiology, ambient PM2.5 levels may be more appropriate exposure estimates than total personal PM2.5 exposure, since the latter reflects a mixture of indoor and outdoor sources.

How a continuous quality improvement plan can reduce the risk of surgical infection in the operating room.

As new technology has pioneered and improved the health care arena, so has change in the Joint Commission on Accreditation of Healthcare Organizations accreditation process. The focus has moved from identifying quality concerns and implying disincentives to that of monitoring and evaluating, using models and teams to address problems identified within accepted processes to quality improvement, improving patient outcomes, and greater job satisfaction among health care staff. The application of the principles of continuous quality improvement create additional paper and work but the results can be a motivated staff that continuously seeks to improve the processes in delivering the highest quality patient care possible. Continuous quality improvement should be reviewed as a positive solution to create change in health care delivery, improving patient outcome, enhance job satisfaction, and as an active approach to meeting quality improvement goals-improved patient outcome.

Development of an intact hepatocyte activation system for routine use with the mouse lymphoma assay.

We have developed a method for cocultivating primary rat hepatocytes with L5178Y/TK+/- -3.7.2C mouse lymphoma cells. This method should provide a means of stimulating more closely in-vivo metabolism compared to metabolism by liver homogenates, while still being useful for routine screening. Hepatocytes were isolated from 200-250 gm adult male Sprague-Dawley rats; 1 X 10(6) viable hepatocytes were seeded per flask. Rapid attachment of the hepatocytes (2 hr) was obtained by using fibronectin-coated 25-cm2 tissue culture flasks. Cocultivated cultures were incubated at 37 degrees C on a platform rocker at 32 oscillations per minute. A 16-hr cocultivated period was selected. With this hepatocyte activation methodology, CP, DMN, DMBA, and B(a)P, genotoxins that require metabolic activation, could be detected as mutagens in L5178Y/TK+/- cells.

High-performance liquid chromatographic assay of biphenyl metabolism by hepatocytes cultured in an embryo/hepatocyte co-culture medium.

A high-performance liquid chromatographic method has been modified for the evaluation of both Phase I and II metabolism of biphenyl by hepatocytes maintained in an embryo/hepatocyte co-culture medium. Extracts of the media, before and after hydrolysis of conjugates, are directly injected onto the HPLC and the major hydroxylated metabolites plus unmetabolized biphenyl are detected by fluorescence after separation under gradient or isocratic conditions. The method is almost free of interferences and is relatively simple and rapid. In the case of the monohydroxylated derivatives, the minimum media concentrations which can be measured are 7 to 20 nM (0.07 to 0.2 pmol on-column). Recoveries from culture medium to which known amounts of biphenyl and metabolites had been added were quantitative (90-103%) and the reproducibility good (interassay CV less than 5%). The assay was applied to cultures of hepatocytes derived from rabbit and from phenobarbital induced and noninduced rat.

Validity of annoyance scores for estimation of long term air pollution exposure in epidemiologic studies: the Swiss Study on Air Pollution and Lung Diseases in Adults (SAPALDIA).

In air pollution epidemiology, estimates of long term exposure are often based on measurements made at one fixed site monitor per area. This may lead to exposure misclassification. The present paper validates a questionnaire-based indicator of ambient air pollution levels and its applicability to assess their within-area variability. Within the framework of the SAPALDIA (Swiss Study on Air Pollution and Lung Diseases in Adults) cross-sectional study (1991), 9,651 participants reported their level of annoyance caused by air pollution on an 11-point scale. This subjective measure was compared with annual mean concentrations of particulate matter less than 10 microm in diameter (PM10) and nitrogen dioxide. The impact of individual factors on reported scores was evaluated. Nitrogen dioxide concentrations at home outdoors (measured in 1993), smoking, workplace dust exposure, and respiratory symptoms were found to be predictors of individual annoyance scores. Regression of population mean annoyance scores against annual mean PM10 and nitrogen dioxide concentrations (measured in 1993 and 1991, respectively) across areas showed a linear relation and strong correlations (r>0.85). Analysis within areas yielded consistent results. The observed associations between subjective and objective air pollution exposure estimates suggest that population mean scores, but not individual scores, may serve as a simple tool for grading air quality within areas. Reported annoyance due to air pollution should be considered an indicator for a complex environmental condition and thus might be used for evaluating the implementation of environmental policies.

Bovine bladder and liver cell and homogenate-mediated mutagenesis of Salmonella typhimurium with aromatic amines.

Comparisons of aromatic amine activation were made by using intact cells or cell homogenates (S-9) from bovine bladder urothelium and liver. Since both liver and bladder are thought to contribute carcinogenic metabolites for bladder cancer initiation, comparisons of these two organs' relative ability to activate aromatic amines to mutagens were made. Salmonella typhimurium mutagenesis was used as an indication of mutagen production. Activation occurred in a dose dependent manner and no mutagenic response occurred unless activating cells or S-9 were present. Bladder urothelial cells metabolically activated the carcinogens, 2-amino-fluorene (AF), 2-acetylaminofluorene (AAF), 4-aminobiphenyl (4ABP), benzidine (BZ), and 2-naphthylamine (2NA) but not 1-naphythylamine (1NA), a non-carcinogen. Liver cells were less active than bladder cells in activating AF and AAF; but there was little or no hepatocyte activation of 4ABP, BZ, 2NA and 1NA. Intact bladder cells were more effective than bladder S-9 in activating AAF, but not in activating AF, 4ABP, BZ and 2NA. The liver S-9 showed more mutagenic activity with AF than did intact liver cells; the reverse was true for AAF, and bovine liver S-9 showed little or no activation of 4ABP, BZ, and 2NA. 1NA was not activated by either S-9 preparation. As was the case for intact cells, bladder S-9 was more effective than liver S-9 in activating the aromatic amines studied. The results demonstrate the capacity of bovine bladder urothelium to metabolically activate aromatic amines and suggest a role for the target organ itself in carcinogen activation. Information on the relative usefulness of intact cells versus S-9 preparations as activation systems was also obtained from these studies.

In vitro embryotoxicity of a series of para-substituted phenols: structure, activity, and correlation with in vivo data.

The embryotoxicity of phenol and twelve para-substituted congeners on mid-gestation rat embryos was evaluated in vitro. Through application of correlative procedures and stepwise regression, equations describing the relationship between physical-chemical properties and various measures of activity were developed. Embryotoxicity was quantified by the log of the reciprocal of the potency estimates for reduction in selected growth parameters and induction of four morphological defects. In general, co-cultured hepatocytes ameliorated embryotoxicity; only phenol-induced embryotoxicity was enhanced by the presence of hepatocytes. In the absence of hepatocytes, measures of growth retardation were positively correlated with molar refractivity of the phenols. With hepatocytes, lipophilicity became important for describing the potential to induce growth deficits. The structural defects had varying correlation patterns in both culture systems. Potencies of these congeners in vitro were also compared to maternal and developmental potencies observed in vivo (Kavlock, Teratology, 41:43-59, '90). Two of the congeners were very toxic in both systems. For the remaining congeners, one maternal toxicity measure was found to be positively correlated with embryotoxicity for growth and development in vitro without hepatocytes. With hepatocytes, a broad spectrum of correlations, both positive and negative, were observed between in vivo developmental toxicity endpoints and in vitro embryotoxicity. Data from preliminary dosimetry studies suggest that phenol congeners may accumulate in embryos exposed in vitro more readily than with in vivo exposure. Potency calculations based on dosimetry information may demonstrate better correlations between data and allow additional relationships between chemical structure and activity to be developed.