The luteolytic effects of prostaglandin (PG) F2α have been described in several laboratory species such as the rat (Gutknecht, Cornette & Pharriss, 1969; Labhsetwar, 1970), hamster (Labhsetwar, 1971; Gutknecht, Wyngarden & Pharriss, 1971), rabbit (Gutknecht et al., 1969) and guinea-pig (Blatchley & Donovan, 1969). This PG also induces ovulation in rats (unpublished observations) and hamsters (Labhsetwar, 1971). If the PG also exerts luteolytic and ovulation-inducing effects in the mouse, this animal might prove to be more economical for experimental purposes because of its smaller size and the limited availability of PG.
Inbred mice of ICI strain were used in this study. Adult females were exposed to males and the day when a vaginal plug was found was regarded as Day 1 of pregnancy. Crystalline PGF2α (racemic) was