Embryotoxic effects of chlorobutanol in cultured mouse embryos

Chlorobutanol (CB) is a commonly used preservative which is added to numerous pharmaceutical preparations, and it is the active ingredient in certain oral sedatives and topical anesthetics. Chlorobutanol has demonstrated adverse effects in adult tissues, but CB has not been previously investigated for its effect on the developing whole embryo. The method of whole-embryo culture was used in this study to expose mouse embryos during two stages of organogenesis to CB at final concentrations of 0 (control), 10, 25, 50, 100, and 200 micrograms/ml. Embryos were evaluated for heart rate (HR), malformations, and somite number, and embryos and visceral yolk sacs (VYSs) were assayed for total protein content as a measure of overall growth. Neurulating (3-6 somite) embryos were malformed and growth retarded by exposure to CB concentrations > or = 25 micrograms/ml, with decreased VYS growth at > or = 50 micrograms/ml and decreased HR at > or = 100 micrograms/ml CB. Early limb-bud stage (20-25 somite) embryos were malformed at CB concentrations > or = 50 micrograms/ml and growth retarded at > or = 100 micrograms/ml, with decreased VYS growth at 200 micrograms/ml and decreased HR at > or = 100 micrograms/ml CB. Thus, CB produces dysmorphogenesis in mouse embryos in vitro, and neurulating embryos are somewhat less sensitive than early limb-bud stage embryos. The concentrations of CB that interfere with normal embryonic development are within the range of human blood levels measured following multiple doses of CB. Preparations containing CB should be used with caution during pregnancy, particularly when repeated dosing may allow accumulation of CB to potentially embryotoxic levels.