The Effects of Length of Exposure to PCB on Circulating Thyroid Hormone Concentration And Ultrasonic Vocalizations in Young Rats

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SUN 366-382-Physiological Impacts of Endocrine Disrupting Chemicals
Sunday, June 16, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SUN-372
Samantha L. King*1, David E. Mankin1, Jeffrey Baldwin1, Howard C. Cromwell1 and Lee A Meserve2
1Bowling Green State University, Bowling Green, OH, 2Bowling Green State Univ, Bowling Green, OH
It has been previously demonstrated that feeding pregnant rats a diet containing polychlorinated biphenyl (PCB) modifies the thyroid status of offspring and the behavioral development of those pups as well as that of the dam.  The literature contains a number of protocols for administration of PCB, and a number of developmental stages during which it has been administered. In the present study, a mixture of PCB 47 (noncoplanar) and 77 (coplanar) congeners were administered at a final dietary concentration of 25 mg/kg of diet, from gestational day 0 to postnatal day (PND) 30, thus providing continuous exposure to PCB of the pups both in utero and ex utero. Comparisons were made between pups from dams given normal diet (control) and those fed the diet described above (PCB), with regard to  thyroid status (circulating T3 and T4 concentrations), and the rate of production of ultrasonic vocalizations (USV/min) as a measure of behavioral development on PND 3, 7, 15, 21 and 30. Overall, T4 was depressed across the examined age range, but this depression only became significant from PND 15 onward (46% of  control on PND 15, 56% on PND 21, and 50% on PND 30.).  Circulating T3 was not significantly altered across the time period, but female pups displayed elevated T3 at 30 days of age (176% of controls). As has been reported by others, USV number per time in the present study steadily declined over the age range, with a significant decline from PND 7 to 21. On the other hand, USV number in the PCB pups increased significantly from PND 3-7, (55%) to a level 218% that of the control group, and then markedly decreased by PND 21 (98%), rather than showing the gradual decline that occurred in control pups. These data may be related to previous PCB effects that have been illustrated during development. Other investigators have found PCB to result in hearing deficits in rat pups. Although not measured in the present study, such depression of auditory acuity may result in an increase in USV number in an effort to communicate with the dam. Also, others have found PCB to increase “high quality” maternal behavior in dams, and the PCB induced elevation of USV number early in life may elicit this modification of maternal behavior.

Nothing to Disclose: SLK, DEM, JB, HCC, LAM

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