CD-109 METABOLISM IN MICE .4. DIET VERSUS MATERNAL STORES AS A SOURCE OF CADMIUM TRANSFER TO MOUSE FETUSES AND PUPS DURING GESTATION AND LACTATION

The transfer of Cd-109 from dam to offspring during gestation and lactation was studied in uniparous mice. From 70 to 210 d of age and during the subsequent reproductive period, young adult female mice received drinking water containing tracer amounts of Cd-109 (8 ppb total Cd) and nutrient-sufficient or -deficient solid diet containing stable Cd (5 ppm Cd). The nutrient quality of the deficient diet was patterned after that consumed by Japanese women who contracted itai-itai disease. To evaluate established maternal stores as a potential source of cadmium transfer to pups, some dams were switched to water with no Cd-109 and diet with an environmental or control level of cadmium (0.25 ppm Cd) during the reproductive period. The resulting pups were analyzed for Cd-109 at birth and at 7-d intervals throughout the lactation period. Pop Cd-109 content at birth, representative of the amount transferred via the placenta during gestation, accounted for less than 1% of the total Cd-109 transferred during the full reproductive period. During lactation, Cd-109 levels in pups from dams with current Cd-109 exposure approximately tripled with each 7-d interval; no significant differences occurred due to nutrient quality of the darns' diet. For 21-d-old pups, 98% of the Cd-109 burden came from the diet of the dam, while only 2% came from her tissue stores, primarily the hepatic one. Such fractions represented a transfer per pup of about 0.01% of the oral Cd-109 dose ingested by the dam during the reproductive period and about 0.05% of the Cd-109 in her tissue stores. Overall, transfer per litter amounted to about 7% of the dietary Cd-109 dose absorbed and retained by the dam during that interval and about 0.2% of the Cd-109 from tissue stores. On lactation d 21, 90% of the total Cd-109 in pups was sequestered in the gastrointestinal tract. Cadmium transfer was additionally examined in multiparous mice that began a repetitive breeding program at 70 d of age at the time of introduction to the same diet/water regimens already described. Overall, females consuming nutrient-sufficient diet experienced 5 consecutive 42-d rounds of gestation/lactation, while their deficient diet counterparts experienced 3 nonconsecutive rounds during an equivalent period. Transfer was examined during their last gestation/lactation experience. Throughout the lactation interval, Cd-109 transfer to pups was about 30% increased for multiparous versus uniparous females; however, transfer again was not significantly affected by nutrient quality of the darns' diet. About 0.02% of the Cd-109 dose ingested by the dam during the last reproductive round was transferred to each 21-d-old pup, while about 0.08% was transferred per litter; approximately 94% of pup whole-body Cd-109 was sequestered in the gastrointestinal tract. These results suggest that the itai factors of multiparity and nutrient-deficient diet did little to increase the small amount of cadmium transferred from Japanese mothers to young during gestation and lactation and that this route of administration was not a significant source of exposure.