Effect of excess dietary methionine on rat pregnancy: influence on ovarian delta5-3beta-hydroxysteroid dehydrogenase activity.

The addition of 4% dl-methionine to a diet of 18% or 12% casein reduced pregnancy maintenance in the rat from 100% to 48% and 5%, respectively. Fetal weight was subnormal. The major influence of methionine was not due to reduced food intake as determined by pair-fed controls but was related to reduced ovarian function. Thus, administration of estrone (0.5 microng) and progesterone (4 mg) on each of days 3 to 20 restored pregnancy to 100% in methionine-fed rats, but fetal weight remained subnormal. Further ovarian delta5-3beta-hydroxysteroid dehydrogenase activity was subnormal in litter-resorbed, methionine-fed rats. Since adequate amounts of ovarian steroids are required for placenta formation, it is possible that placental development was impaired and served as the cause of fetal wastage in animals consuming excess methionine.