17β-estradiol exposure accelerates skeletal development in Xenopus laevis tadpoles

Although it is well established that estrogen regulates skeletal growth and ossification in mammals, the effects of estrogen on skeletal development in amphibians are relatively uncharacterized. This study was conducted to characterize the impact of 17β-estradiol exposure on skeletal development in Xenopus laevis tadpoles. On day 48 postfertilization, tadpoles were placed in tanks containing 50% Holtfreter's Solution ±17β-estradiol at one of four concentrations (10(-11), 10(-10), 10(-9), and 10(-8) M). At 7-11 day intervals until day 91, 7-10 tadpoles per group were killed, fixed, measured, and staged. Specimens were then cleared and double-stained for cartilage and bone, and 34 skeletal elements were analyzed for ossification. Results from the study indicate that both low (10(-11) M) and high (10(-8) M) concentrations of 17β-estradiol have a significant stimulatory effect on tadpole development. Both the larval stage and ossification index of tadpoles exposed to 10(-11) or 10(-8) M 17β-estradiol were significantly greater than those observed in control animals by day 91 postfertilization. These results are consistent with the hypothesis that endogenous and exogenous estrogen could play a role in the regulation of bone ossification in amphibians.