Effects of lead and hyperthermia on prenatal brain growth of guinea pigs

The effects of lead at blood levels of 100 micrograms/100ml or less on the brains of young animals have not been clearly defined, and little is known of its effects and interactions with other agents on prenatal brain development. This study examined the effects of subclinical doses of lead acetate given to pregnant guinea pigs on the development of the embryo brain. At 9 A.M. on day 20 or 21 of pregnancy, guinea pigs were given 6, 12.5, or 25 mg/kg body weight of 0.5% lead acetate in distilled water by intraperitoneal injection. Some of the animals at each dose rate were also exposed to hyperthermia at 11 A.M. on the day of injection and the following day. Another group was exposed to hyperthermia without lead treatment. A saline-treated control group was used for comparison. Mean levels of lead in blood 1 hour after dosing ranged between 65 and 128 micrograms/100 ml and at 24 and 72 hours between 65 and 96 micrograms/100 ml. Brain weights of newborn guinea pigs in the 12.5- and 25-mg lead acetate group were significantly reduced compared with control values. Body weights of all groups receiving lead were not significantly different from those of controls. There was no indication of interaction between hyperthermia and lead acetate in doses of 6 or 12.5 mg/kg. At 25 mg/kg plus hyperthermia, there appeared to be a strong synergistic response, with an incidence of 88% micrencephaly compared with 5% in the group given 25 mg/kg without hyperthermia and 46% in the hyperthermia without lead group.(ABSTRACT TRUNCATED AT 250 WORDS)