Exposure to Low Concentrations of Di-n-butyl Phthalate During Embryogenesis Reduces Survivability and Impairs Development of Xenopus Laevis Frogs

Abstract

Di-n-butyl phthalate (DBP) appears to be a ubiquitous environmental contaminant, as indicated by its presence in air, water, and soil worldwide (Giam et al., 1980; ATSDR, 2001; Peterson & Freeman, 1982) and the presence of its major metabolite, monobutyl phthalate (MBP), in random human urine samples (Blount et al., 2000). Studies indicate that exposure to a variety of endocrine-disrupting chemicals, such as DBP, may be partially responsible for reported global amphibian declines; if so, amphibians may serve as ecological harbingers for the future of human health. Therefore, this study was undertaken to investigate the effects of environmentally relevant concentrations of DBP on development in Xenopus laevis African clawed frogs. Developmental effects of DBP on Xenopus embryos were determined using the 96-h frog embryo teratogenesis assay-Xenopus (FETAX). Embryos (n = 300/group) were exposed from gastrulation (stage 8-11) through primary organogenesis (stage 46) to 0.1, 0.5, 1, 5, 10, or 15 ppm DBP dissolved in 0.01% dimethyl sulfoxide (DMSO), vehicle alone (0.01% DMSO; solvent control), or FETAX culture medium only (control; n = 600). At 96 h, mortalities for control, solvent control, and 0.1, 0.5, 1, 5, 10, and 15 ppm DBP were 5, 4, 6, 5, 5, 9, 18, and 52%, respectively; the incidence of developmental malformations in the surviving tadpoles was 7, 9, 15, 37, 51, 53, 90, and 100%. The average length of embryos was significantly lower in all DBP treatment groups. Thus, DBP significantly affected development of Xenopus embryos at low, environmentally relevant concentrations.

Exposure Levels of Environmental Endocrine Disruptors in Mother-Newborn Pairs in China and Their Placental Transfer Characteristics

“…The median concentrations of the MEHP, OP, 4-NP and PBDEs in our study were much higher than the results of previous studies. Phthalates are widely used in commercial products, as plastic softeners and solvents in personal care products, lubricants and insect repellents [32]–[34]. Potential sources of exposure for DEHP include polyvinylchloride containing medical devices, food packaging, plastic toys, furniture, and car upholstery.…”

Thyroid Disruption by Di-n-Butyl Phthalate (DBP) and Mono-n-Butyl Phthalate (MBP) in Xenopus laevis

“…Based on this knowledge, metamorphic development of X. laevis has been proposed as a unique biological system to specifically investigate EDC effects on thyroid hormone action [21], [22]. Studies of Lee et al [23] indicated that DBP significantly affected development of X. laevis embryos at low, environmentally relevant concentrations. However, there have been few reports concerning the effects of DBP and MBP on metamorphosis of X. laevis and the molecular mechanisms of thyroid system disruption.…”

Lethal and sublethal effects of phthalate diesters in Silurana tropicalis larvae

“…Similarly, studies have reported that the plastic additives bisphenol A (BPA), tetrabromobisphenol A, and phthalic acid led to edema in African clawed frog and zebrafish embryos . Cardiac abnormalities were also more frequent in tadpoles treated with 15 mg/L DBP . The increases in lethality and malformations observed in the DCHP treatments were concurrent with increases in hsp70 mRNA levels.…”

“…Similarly, DEHP reportedly suppressed medaka embryo development [38]. African clawed frog tadpoles acutely exposed to 0.1 mg/L or 15 mg/L DBP also experienced significant reductions in body lengths [6,39]. It is well known that amphibian development is highly dependent on thyroid hormones.…”