Friday, 9 September 2005

This presentation is part of: AMS in Low Dose Biosciences Posters

Measuring Transfer of 14C-PCB from Diet to Maternal Milk in a Goat Model Using an Accelerator Mass Spectrometer (AMS)

Elsa M. Janle1, Janice E. Sojka2, George S. Jackson3, and Charles R. Santerre1. (1) Foods and Nutrition, Purdue University, 700 W. State St., West Lafayette, IN 47907-2059, (2) Veterinary Clinical Sciences, Purdue University, 625 Harrison Street, West Lafayette, IN 47907, (3) Physics, Purdue University, 525 Northwestern Ave, West Lafayette, IN 47907-2036

Environmental pollutants pose a substantial risk to nursing infants. Many of these toxicants (i.e., PCBs, PBDEs, mercury) are passed from the diet of the nursing mother to the infant through breast milk. Determining the toxicokinetics involving the GI absorption and excretion in maternal milk has been difficult to measure in humans due to ethical limitations. However, newer technologies that enable measurement of very low levels of radioisotopes and the development of superior animal models will help us to predict the relationship between maternal dietary intake and excretion in milk. Understanding the toxicokinetics allows for improved risk assessment which is necessary to protect the nursing infant from exposure to environmental pollutants.

A goat model was developed and a 14C labeled PCB (2,2',4,4',5,5'-hexachlorobiphenyl-UL-14C ) was used as a tracer. Use of a labeled compound makes it possible to track the absorption distribution and elimination of the compound over a background of similar compounds already present from environmental exposure. A one-year-old, 45 Kg lactating Nubian doe who had kidded 2 ½ months previously was milked twice a day to maintain lactation. Baseline milk samples were collected for 3 days. The goat was dosed orally with .084 mg of labeled PCBs. The dose contained 3 uCi of 14C (66 nCi/Kg). Blood and milk samples were collected for 2 months after dosing. The 14C/12C (10-15) ratio of the milk samples reached a peak value of 1.69 x 105 in the milk on the second day after dosing and then declined to about 1 x 104 about three weeks after dosing and remained fairly stable until the end of the two month period. The 14C/12C (10-15) ratio of plasma samples rose slowly reaching a peak value of 1.930E+04 at 24 hours. Plasma counts declined slowly. By the third week plasma and milk counts were approximately the same.

The results of this study indicated that it would be possible to use a lower dose of labeled PCB because of the extreme sensitivity of the AMS measurements. Thus, the potential exists for developing methods to study the toxicokinetics and transfer to milk in humans using radiologically and toxicologically benign doses of environmental toxins.


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