Effects of Subcutaneously Injected Graded Doses of All-Trans Retinoic Acid and All-Trans Retinoyl beta-Glucuronide on the Outcome of Pregnancy in Sprague-Dawley Rats

The effects of single subcutaneous injections (sc) of graded doses (20, 40, 80, 160, 320, and 480 mumol/kg body weight (BW) of all-trans retinoic acid (RA) and all-trans retinoyl beta-glucuronide (RAG) on day 8.5 of gestation on the outcome of pregnancy in Sprague-Dawley rats was studied. At dose levels of 20, 40, and 80 mumol/kg BW, neither RA nor RAG showed any adverse maternal or fetal effects. However, at dose levels of 160, 320, and 480 mumol/kg, RA was found to be much more toxic than RAG to both mother and fetus. Fetuses of animals receiving a 160 mumol/ kg BW dose of RA were significantly reduced in weight and length, while animals receiving the same dose of RAG had fetuses of normal size. RA doses of 320 and 480 mumol/ kg BW resulted in symptoms of maternal toxicity and even death. In contrast, RAG at these high levels produced no signs of maternal toxicity. RAG doses of 320 and 480 mumol/ kg BW were also less toxic to fetuses. RA doses of 320 mumol/kg BW resulted in only 8% live births, while animals treated with an equivalent amount of RAG experienced 95% live births. Animals receiving a dose of 480 mumol/kg BW of RA had no live births, but similar doses of RAG resulted in 28% live births and pups of normal size.