Effects of age at unilateral ovariectomy on compensatory responses of remaining ovary in rabbits.

Abstract

Effects of age at unilateral ovariectomy (ULO) on compensatory responses of the remaining ovary were examined in rabbits. ULO was performed on 8 does for each group at 30 (group 30), 90 (group 90), 160 (group 160) and 230 days of age (group 230). Eight intact does were served as controls. Four does of each group were laparotomized and remaining ovaries were removed at first estrus (over 250 days of age). Numbers of large follicles on ovarian surface ( ?? 1.5 mm in diameter) per doe in all groups were nearly 10 and these values of ULO groups were twice as large as controls. Mean ovarian weight and volume of group 90 were the highest, and those of group 30 were second. The values in these ULO groups showed significant differences in comparison with controls. In histology of these ovaries, numbers of large, healthy follicles ( ?? 1 mm in diameter) per ovary in ULO groups were roughly double compared with those in controls. There was a tendency that the number of small, atretic antral follicles (< 1 mm in diameter) was increased in ULO animals operated at young age. The number of atretic antral follicles was closely correlated with ovarian weight and volume. To induce ovu-lation, the remaining 4 does of each group were injected with 20 IU of hCG. The num-bers of corpora lutea per doe of all groups were about 10 with no significant difference among groups. These results suggest that ULO in the immature period induces marked compensatory hypertrophy after puberty and that, regardless of age at ULO, the re-maining ovary in the ULO animal fulfills the function of both ovaries in the intact animal.