ANTI-OVULATORY POTENCY OF VARIOUS STEROIDS, DETERMINED BY SINGLE INJECTION INTO FEMALE HAMSTERS

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Abstract
SUMMARY: Hamsters injected at metoestrus (day 1) and killed at day 2 of the next oestrous cycle were used to determine the ovulation-inhibiting potency of various steroids. Oestradiol and testosterone prevented ovulation by inducing atresia in the developing follicles which would have normally ovulated. Esterification of oestradiol markedly increased its anti-ovulatory activity. The progestational steroids usually acted on the final phases of follicular maturation rather than affecting earlier phases of growth. The most potent pure gestagen tested was 6,7α-dimethyl-6-dehydroprogesterone which was five times as active as progesterone or norethindrone in preventing ovulation of ripe follicles. Ethynodiol diacetate also blocked ovulation of mature follicles, but with increased doses atresia became the primary mechanism responsible for inhibiting ovulation. The latter effect is probably due to inherent oestrogenicity of the compound. The advantages of this method as a screening procedure for anti-ovulatory activity are discussed.