Abstract
Hamster embryos in utero on the 11th or 12th day of gestation were treated simultaneously with aminopyrine (Ap) and sodium nitrite (NaNO2) by oral administration of the compounds to the mothers by stomach tube. For measurement of induction of 8 AG-resistant mutations, the embryonic cells from treated and control mothers were cultured in MEM plus 10% FBS for 72 h and then selected in medium containing 10 or 20 microgram/ml of 8 AG. The number of 8 AG-resistant colonies was markedly increased after co-administration of Ap and NaNO2, and slight induction of mutations was also observed in cells from mothers given NaNO2 alone. This treatment also caused morphological or malignant transformation of cultured cells. About 5- to 6-fold increase in the number of transformed colonies was observed in cells from mothers given Ap plus NaNO2. Cells from the transformed colonies produced tumors when implanted into the cheek pouches of young golden hamsters. These tumors were diagnosed as pleomorphic fibrosarcomas. Similar results were obtained with cells from embryos treated transplacentally with NDMA as positive controls. A single transplacental oral application of Ap at 200 mg/kg or of NaNO2 had only slight biological actions to the cultured embryonic cells. NDMA was produced in the stomach of animals treated simultaneously with Ap and NaNO2. A small amount of NDMA was also detected in the stomach after a single dose of NaNO2.