Effect of salicylamide on the placental transfer and fetal tissue distribution of sodium-35S-sulfate in the rat

Pregnant rats were used to determine effects of salicylamide on the sequential uptake and loss of radiosulfate by maternal and fetal tissues. Separate and combined effects of salicylamide and protein restrictions on radiosulfate retention by fetal rat tissues were determined. Rats were fed salicylamide-containing or control diets from the 4th or 6th day of gestation. Rats were killed between the 17th and 19th days of gestation, following intramuscular injection of sodium-35S-sulfate. Fetal and placental radiosulfate uptake was related to maternal serum levels. Salicylamide administration decreased radiosulfate uptake by maternal serum and liver, fetus and placenta--effects being dose-dependent. Differences in radiosulfate uptake by the fetus and placenta over time, induced by salicylamide, were also significant independently of maternal serum levels of radiosulfate. Major retention of 35S was found in the fetal cartilage with lower concentrations in the fetal skin, intestine, brain and liver. Protein restriction increased retention of 35S, and salicylamide administration caused a significant reduction in 35S retention by fetal tissues. Skeletal malformations were found in fetuses from dams receiving salicylamide. It is concluded that this drug lowers the availability of sulfate to the fetus from the dam, impairs the incorporation of sulfate by fetal tissues utilizing sulfates, and is teratogenic.