Abstract
Summary
The embryolethal and teratogenic effects of actinomycin D were studied in Long-Evans rats. Subcutaneous administration extended the teratogenic time range of the drug beyond that previously identified by intraperitoneal injections; a single dose (200 μg/kg body weight) given on day 12 of pregnancy caused club foot, generalized edema, exomphalos, and growth retardation in 14% of surviving young. When equal amounts of L-thyroxine were injected concurrently with actinomycin D on day 12 of development, the effects of actinomycin on the mothers were ameliorated and abnormalities in the young were strikingly reduced. When injected one day previous to treatment with actinomycin D, thyroxine prevented fetal malformations. These results may be interpreted on the hypothesis that the hormone forms a harmless complex with actinomycin D.
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