Hydroquinone: A Developmental Toxicity Study in Rats

Abstract

To determine the potential developmental toxicity of hydroquinone (HQ), pregnant rats (COBS-CD-BR) were given 0, 30, 100, or 300 mg/kg HQ by gavage on the 6th through the 15th days of gestation. Maternal effects included a slight, but significant (p ≤ 0.05), reduction in body weight gain and feed consumption for the 300 mg/kg HQ dams. Reproductive indices, i.e., pregnancy rate, numbers of corpora lutea, implantation sites, viable fetuses, and early and late resorptions, fetal sex ratio, pre-and postimplantation losses, and gravid uterine weights, were not affected by treatment with HQ. A slightly reduced (p ≤ 0.05) mean fetal body weight seen at the 300 mg/kg dose level was associated with the slightly reduced body weight gain seen for the dams at this dose level. Gross external, internal soft tissue, and skeletal examinations of the fetuses revealed no HQ-related malformations. The incidences of gross external variations (small hematomas) and internal soft tissue variations (dilated renal pelvis, hydronephrosis, and hydroureter) in the HQ-treated litters were not statistically different from the control incidences. Skeletal variations (delayed ossification of membranous skull bones, hyoid bone, thoracic centra 1–3, sacral arches 3 and 4, and bilobed thoracic centra 9–13) were seen with similar frequency in the control and HQ-treated groups. A statistically significant increase in the incidence of total common vertebral variations seen at the 300 mg/kg HQ dose level was not considered toxicologically significant. The incidences of total skeletal variations were not statistically different between the control and the HQ-treated groups. It is concluded that HQ was not selectively toxic to the developing rat conceptus and, thus, appears not to have the properties of a developmental toxicant. The no-observable-effect level for both maternal and developmental toxicity was 100 mg/kg, whereas 300 mg/kg was the no-observable-adverse-effect level.