Most ovarian follicles degenerate in a process
called atresia, but the precise mechanisms behind
this process remain unclear. We have investigated
the roles of cyclooxygenase-2 and prostaglandin E
2
in the atresia of preovulatory follicles in immature
rats primed with pregnant mare’s serum
gonadotropin. Massive atresia was histologically
confirmed to occur in preovulatory follicles of
control rats. In contrast, administration of NS398, a
specific cyclooxygenase-2 inhibitor, caused
luteinization resulting in development of apparently
normal corpora lutea and also atypical membranous
corpora lutea. Progesterone secretion was
high in the plasma of these rats, indicating that the
corpora lutea were functional. These data suggest
that cyclooxygenase-2 may be involved in determining
whether the fate of preovulatory follicles will
be atresia or luteinization.
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