MP10 PCB Toxicity in Aquatic Organisms- Endocrine Effects
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(KHA-1117-838618) Neuroendocrine Toxicity of Aroclor 1254 and Selected PCB Congeners in Atlantic Croaker.

Khan, I¹, Berg, H¹, Thomas, P¹, ¹ The University of Texas at Austin, Marine Science Institute, Port Aransas, TX, USA

ABSTRACT- Aroclor 1254 has been shown to impair reproductive neuroendocrine function in the Atlantic croaker, Micropogonias undulatus. In addition, we have identified hypothalamic tryptophan hydroxylase (TPH), the rate-limiting enzyme in serotonin synthesis, as a target of PCB neuroendocrine toxicity. A previous study in rats has implicated di-ortho-substituted non-coplanar PCB congeners in the inhibition of a similar enzyme, tyrosine hydroxylase, which is the rate-limiting enzyme in dopamine synthesis. Therefore, the present study was designed to investigate whether di-ortho-substituted congeners (PCB 47, PCB 153) or a coplanar congener (PCB 77) present in Aroclor 1254 could be responsible for reproductive impairment observed in croaker exposed to the PCB mixture. Fish were exposed to PCB 47 and PCB 153 in the diet (0, 0.2 and 1.0 mg/kg body weight/day) for 30 days and to PCB 77 (0.01 and 0.1 mg/kg body weight/day) for 15 days. Neither PCB 47 nor PCB 153 altered hypothalamic TPH activity or gonadal growth in croaker at doses similar to the effective doses of the Aroclor 1254 mixture. Therefore, these ortho--substituted PCB congeners known to be neurotoxic in mammalian systems are unlikely to contribute to Aroclor1254-induced reproductive neuroendocrine disruption in croaker. In contrast, PCB 77 significantly inhibited hypothalamic TPH activity and gonadal growth at doses much lower than the effective doses of Aroclor 1254. Interestingly, the decreases in TPH activity after Aroclor 1254 and PCB 77 exposures were not accompanied by reduced TPH protein content. Thus, the decrease in TPH activity does not appear to be caused by alterations in TPH protein and may involve other modes of TPH inactivation. The results provide first evidence for the disruption of reproductive neuroendocrine function by a coplanar PCB congener and may suggest involvement of oxidative processes in PCB neuroendocrine toxicity.

Key words: neuroendocrine toxicity, tryptophan hydroxylase, polychlorinated biphenyls, Atlantic croaker