Locoweed embryotoxicity in rats.

In an effort to develop a laboratory animal assay for locoweed (Astragalus lentiginosus and Astragalus wootoni) teratogenicity, different amounts of the plant were administered either in feed pellets or by gavage to rats. In preliminary experiments with A. lentiginosus in feed pellets, we found dose-dependent effects on the number of pups born alive and on birth weight of pups. In the primary experiment, 1 gm of A. lentiginosus or A. wootoni administered by gavage on Days 7 through 17 of gestation produced similar results. A. lentiginosus reduced pup birth weights by 13% less than that of controls; this weight differential persisted for at least 4 weeks. A. lentiginosus also reduced the number of offspring born alive (34.9% fewer than those of controls) and the number of survivors to weaning (86.4% fewer than that of controls). No gross malformations were observed. Behavioral tests, however, showed that activity patterns of 30-day-old offspring of dams fed locoweed differed from those of pups of control dams. A test of learning indicated no differences. At 80 days of age, offspring of treated dams showed no significant differences from those of control dams. The same behavioral tests also showed no differences among the dams at the time of testing. Microscopic examination of tissues from pups whose mothers had been given locoweed revealed lesions only in the newborn pups. Neural lesions were not observed even in the newborn pups. Dose-dependent and species-dependent embryotoxic effects of locoweed were observed in rats.