Sodium pentobarbital-induced mutations in the hamster.

When virgin Syrian hamsters aged 6 to 8 wk were mated during estrus and anesthetized with sodium pentobarbital (Nembutal) 4 to 5 hr before estimated ovulation, pregnancy wastage in the newly conceived litter was observed. This was manifested by polyspermy of moribund eggs and death of fertilized eggs, deficits of expected zygotes, and triploidy and tetraploidy in 3-day-old surviving embryos. Multiple factors determined the nature of this wastage, including dosage of Nembutal [sodium 5-ethyl-5-(1-methyl butal) barbiturate], route of its administration, degree of resulting respiratory depression, and ultimately a pH imbalance (below 7) in the mother. Polyspermy appeared to result from the penetration of degenerating ova by 10-20 sperm, triploidy to polar body retention, and tetraploidy to endoreduplication of chromosomes before cell cleavage; identification of 2N/4N mosaics supports this inference.