Cytogenetic evaluation of di-(2-ethylhexyl)phthalate and its major metabolites in Fischer 344 rats.

Di-(2-ethylhexyl)phthalate (DEHP) and its two major metabolites, mono-(2-ethylhexyl)phthalate (MEHP) and 2-ethylhexanol (EH), were evaluated for their ability to induce chromosomal damage in male Fischer 344 rats after oral administration. Dose levels, the highest of which represents one-tenth of the five-day LD50, were based on a preliminary five-day dose-finding study for each test material. The dose levels selected were 5.0, 1.7, and 0.5 ml/kg/day for DEHP; 0.14, 0.05 and 0.01 ml/kg/day for MEHP; and 0.21, 0.07 and 0.02 ml/kg/day for EH. All test materials and vehicle control (corn oil) were administered by gavage for five consecutive days. A triethylenemelamine (TEM)-positive control group received a single intraperitoneal injection of 0.5 mg/kg TEM one day prior to sacrifice. Of the 50 metaphase bone marrow cells examined from each animal, no significant increase in chromatid and chromosome breaks or structural rearrangements were noted for DEHP, MEHP, and EH. In addition, the mitotic index, determined from 100 cells per animal, was unaffected by DEHP, MEHP, or EH. The results of this investigation indicate that DEHP, MEHP, and EH, at these dose levels, did not induce detectable chromosomal aberrations after oral administration.