Test of six chemicals for embryotoxicity using fetal mouse salivary glands in culture

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Abstract
Many new chemicals come into use each year, and the need for rapid and cost‐effective methods for testing developmental toxicity is apparent. Establishing reliable in vitro techniques is important to a tier approach to testing for developmental toxicity. The fetal mouse salivary gland was selected as a possible test system because several interacting developmental processes occur in gland growth, and development is quantifiable by counting lobes. For each chemical tested, 20 glands from 13‐day embryos were treated in a control media and in three concentrations of the test chemicals. The number of lobes present after 48 hours is dependent on the number of lobes at explanation. Glands with different numbers of lobes at explantation were compared by dividing the number of lobes present after 48 hours by the number present at explantation to determine a growth ratio. Mean growth ratios were used to construct dose‐response curves, and from these curves the concentration that reduced growth by 50% (TP50) was determined. Comparisons with in vivo data were made by calculating three ratios; the TP50 was divided into the lowest teratogenic dose, the lowest maternal toxic dose, and the dose that was lethal to 50%. Four in vivo teratogens, 6‐aminonicotinamide, cytochalasin B, hydroxyurea, and 3‐acetylpyridine, all had ratios much higher than 1, indicating a very sensitive response by the glands. One in vivo teratogen, dexamethasone, had much lower ratios, indicating less sensitivity. Acetaminophen, a nonteratogen in vivo, actually stimulated growth of the glands at 10−5 M and had very low ratios indicating a minimal response by the glands.