The causes of perinatal death induced by prenatal exposure of rats to the pesticide, mirex. part II: Postnatal observations

Abstract

Prenatal exposure to mirex induces a high rate of perinatal death without obvious cause. Part I of this study (Grabowski and Payne, 1982), in which fetuses were exposed to a moderate dose of mirex and observed just prior to parturition, it was found that 14% had died recently and an additional 9% were apparently dying with serious cardiovascular symptoms. In the present study, electrocardiograms of normal (oil‐fed controls) and mirex‐exposed rats (6 mg/kg·d of insecticide on d 8 to 15 of gestation) were obtained at birth and for several days afterwards. An ECG was obtained from most individuals within 5 min of birth. Pups were then weighed and tattooed so that individuals could be followed to postnatal d 5. Data on 70 control newborns were compared with that on 131 mirex‐treated pups. In the treated group, 23% were stillborn. Of those born alive, 8% died within 6 h of birth, and another 13% within 48 h. At birth, 14% had first‐degree heart blocks, and 2% had second‐degree blocks. All of those with second‐...