EFFECT OF DIETHYLSTILBESTROL OR ZERANOL ON FETAL DEVELOPMENT, GESTATION DURATION, AND NUMBER OF OFFSPRING IN NMRI MICE

Objective-To evaluate the effects of diethylstilbestrol (DES) or alpha -zearalanol (zeranol) on fetal development, gestation duration, and nu mber of offspring. Design-Study effects of prenatal administration of DES or zeranol on various pre- and perinatal variables in an experimen tal group of mice, compared with effects in a control group. Animals-P regnant NMRI mice. Procedure-Diethylstilbestrol or zeranol (150 mg/kg of body weight) or vehicle (controls) was administered sc to pregnant mice on days 9 and 10 of gestation. Fetuses from pregnant mice of each group were counted and weighed, and their size and head length were r ecorded. Additional pregnant mice delivered their fetuses naturally, a nd pups from each group were counted and their sex was determined. At the end of gestation, abortions were evaluated. All data were statisti cally analyzed. Results-Mean number of fetuses was significantly lower (P < 0.0001) in DES-treated (4.59 +/- 0.48) than in control mice (8.3 3 +/- 0.49). Both estrogenic substances significantly reduced fetal si ze and weight (P ( 0.0001), compared with control mice. Diethylstilbes trol significantly increased abortion frequency (P < 0.0001) and gesta tion duration (P < 0.0001), compared with values for control mice. A r educed number of live pups (P < 0.0001) from pregnant mice administere d DES (5.48 +/- 0.38) or zeranol (5.97 +/- 0.49) was observed, compare d with control mice (8.52 +/- 0.50), because of reduced number of male offspring (P < 0.0001). Conclusions-Diethylstilbestrol or zeranol adm inistered during mid-pregnancy leads to decreased fetal weight and siz e and lower numbers of male offspring at birth. Likewise, DES induced a significant increase in abortions and gestation duration.