Acute and subacute toxicity in Sherman strain rats exposed to 4,4'- and 2,2'-dipyridyl.

Acute and subacute toxicity was studied in adult Sherman strain rats exposed to 4,4'-and 2,2'-dipyridyl. The single oral LD50 for 4,4'-dipyridyl was 175 mg/kg in male and 172 mg/kg in female rats; for 2,2'-dipyridyl it was 100 and 107 mg/kg, respectively. Symptoms of toxicity for 4,4'-dipyridyl included subdued behavior, red stains around mouth and eyes, lacrimation, swelling around the eyes, and occasional convulsions. Rats receiving 2,2'-dipyridyl had subdued behavior, loss of muscle coordination, red urine, tremors, and convulsions. Onset of symptoms was rapid, and most rats died from internal hemorrhage within 2 d after dosing. Rats given lower single oral doses of 90 mg/kg 2,2'-dipyridyl and 155 mg/kg 4,4'-dipyridyl had no symptoms and no organic pathology 2 wk after dosing. Rats given doses of 5.1 and 25.5 mg/kg 4,4'-dipyridyl and 7.13 and 35.6 mg/kg 2,2'-dipyridyl in their drinking water for 3 mo showed no significant effects that could be related to the consumption of dipyridyl.