Cycling of Cycasin from Newborn Rats to Their Mother and Back to the Newborn ∗

Summary

Day-old-rats injected subcutaneously once with saline, 2.5 or 5.0 mg of cycasin and returned to their dam developed kidney and liver tumors later in life. It is suggested that the lesions seen in these rats resulted from the ingestion by the dam of the cycasin excreted in the pups' urine. The urine was probably consumed by the dam when she licked and groomed her pups. The cycasin was then degraded to MAM, the presumed carcinogen, by the bacteria in the dam's intestinal tract. MAM and the cycasin that escaped deglucosylation were then returned to the pups via the dam's milk. By this means, the saline as well as the cycasin injected pups were exposed to the carcinogen. In separate studies, day-old rats excreted within 7 hrs up to 33% of 5.0 mg of cycasin injected subcutaneously. This rate increased to 50-60% in 2-day-old pups and sometime after day 7 of life, 100% of a 20-mg dose could be recovered in the urine within 7 hr.