Effects of estrogen, antistrogen, and feeding on egg maintenance in the leopard frog.

Abstract

The effects of estrogen on egg maintenance were tested in gravid female frogs by injecting them with 0.5 ug estradiol-17B per gram of body weight. Upon autopsy, the animals were found to have greater degeneration of the oocytes, as indexed by absence of the germinal vesicle and pigment mottling, than did the control animals. Experimental animals autopsied 6 days after treatment had more degeneration than those autopsied at 2 days. To determine if endogenous estrogens could also cause degeneration of mature oocytes, an antiestrogen, nafoxidine, was administered in a dosage of 5 ug per gram body weight to gravid female frogs. This was done with spring animals coming out of hibernation and fall animals going into hibernation. Half the experimental and controls were fed and the other half were not fed during the treatment period. Hormone treatment was repeated twice weekly, and the animals were autopsied at the end of 3 weeks time. Nafoxidine treated animals were found to have less degeneration of mature oocytes than were control animals in both spring and fall samples. Additionally, animals who were not fed appeared to have healthier eggs than those animals who were fed. However, the feeding effect was not statistically significant in this sample. Blood studies on the nafoxidine and control animals from the spring sample show no significant differences in hematocrit, total blood proteins, or blood plasma estradiol-l7B levels.