Distribution of 14C-labelled acrylamide and betaine in foetuses of rats, rabbits, beagle dogs and miniature pigs

Abstract [ 14 C]Acrylamide and [ 14 C]betaine hydrochloride were administered in a single iv dose to pregnant rats, rabbits, beagles dogs and miniature pigs late in gestation (1–2 days before expected parturition). Dosages used were 10 mg/kg for rats and 5 mg/kg for the other species. The compounds were allowed to equilibrate in the animal (for 1 hr in rats and for 2 hr in the other species); the dam was then killed and the foetuses were removed by caesarean section. Each foetus was weighed and analysed for radioactivity, either by homogenization of the whole foetus (rat and rabbit) or by determining separately the radioactivity in individual organs and tissues (dog and pig). Foetal uptake of the polar compound betaine hydrochloride was much lower than that of the more lipophilic acrylamide. The sex of the foetus did not appear to affect uptake of either compound. There were no significant differences in total uptake of isotope attributable to the position of the foetus within the uterus in any of the four species given either acrylamide or betaine. Similarly, uterine position did not affect the uptake of acrylamide or betaine by individual tissues of foetal dogs or pigs. Since the distributions of 14 C-labelled acrylamide and betaine hydrochloride were essentially uniform throughout a litter, it would not be necessary to sample all of the members of a litter to obtain a representative picture of foetal distribution.