Teratogenic Effects of Organohalogen Contaminants Extracted from Whale Bacon in a Whole-Rat-Embryo Culture System

Abstract

Marine foods can be contaminated with organochlorines and the risk to human beings who consume these foods needs to be evaluated. We examined the teratogenic effects of contaminants extracted from whale bacon on rat embryos using a whole-embryo culture system. Embryonic day 11.5 embryos were cultured for 48 h with organohalogens extracted from whale bacon at low (polychlorinated biphenyls (PCBs): 0.32 ppm, dichlorodiphenyltrichloroethanes (DDTs): 0.16 ppm, chlordanes (CHLs): 0.02 ppm) and high (PCBs: 2.15 ppm, DDTs: 1.99 ppm, CHLs: 0.20 ppm) doses. The levels of organohalogen compounds in cultured embryos were determined. The organochlorine contaminants extracted from whale products were readily transferred to the cultured rat embryos. The number of heartbeats, yolk sac circulation score, and embryonic body circulation score of embryos did not change during the culture period in either exposure group. Cultured embryos treated with the low-dose contaminated medium for 48 h showed abnormalities of the mandible, and craniofacial or forelimb hematomas with an incidence of 50%. All embryos treated with the high-dose medium showed craniofacial abnormalities and cleft lip, and limb abnormalities and hematomas. These results indicate that the organohalogen contaminants in whale bacon may be teratogenic in a dose-dependent manner. Further studies are necessary to determine the dose-effect relationship.

Keywords: morphological abnormality; polychlorinated biphenyl; rat embryo; whale bacon; whole-embryo culture.

Figure 1

Major congener profiles of organohalogens in the culture medium and embryos with low- and high-dose exposure. E11.5 rat embryos were cultured for 48 h at 38 °C by rotating in 100% rat serum. Each column represents the mean ± S.D. (vertical bars) for four embryos. PCB 101, 2,2′,4,5,5′-pentachlorobiphenyl; PCB 118, 2,3′,4,4′,5-pentachlorobiphenyl; PCB 138, 2,2′,3,4,4′,5′-hexachlorobiphenyl; PCB 153, 2,2′,4,4′,5,5′-hexachlorobiphenyl; PCB 170, 2,2′,3,3′,4,4′,5-heptachlorobiphenyl; PCB 180, 2,2′,3,4,4′,5,5′-heptachlorobiphenyl; p,p′-DDE, 1,1-bis(4-chlorophenyl)-2,2-dichloroethylene; p,p′-DDT, 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane; t-Nonachlor, trans-nonachlor.

Figure 2

Morphological changes of rat embryos cultured in the control medium. (1) Whole rat embryo without the placenta and yolk sac isolated from the uterus (incubation time = 0). (2) Whole rat embryo with the placenta and yolk sac cultured for 24 h. (3) Whole rat embryo with the placenta and yolk sac cultured for 48 h. Scale bar = 1 mm.

Figure 3

Morphological changes in rat embryos cultured for 24 h with low- and high-dose organohalogen contaminants from whale bacon. Whole cultured rat embryos with placenta and yolk sac. Scale bar = 1 mm.

Figure 4

Morphological changes in rat embryos cultured for 48 h with low- and high-dose organohalogen contaminants from whale bacon. Whole cultured rat embryos with placenta and yolk sac. Scale bar = 1 mm.

Figure 5

Morphological changes in rat embryos cultured for 48 h with low- and high-dose organohalogen contaminants from whale bacon. Whole cultured rat embryos without placenta and yolk sac. Scale bar = 1 mm.

Figure 6

The rates of morphogenic abnormalities in rat embryos (n = 12) cultured for 48 h with low- and high-dose organohalogen contaminants from whale bacon. Number of embryos: control (without vehicle), 8; control (with vehicle), 8; low-dose exposure, 16; high-dose exposure, 17. The morphogenic abnormalities observed were abnormalities of the telencephalon, mandible or tail, including cleft lip, and craniofacial and forelimb hematomas.