Effect of dietary Senecio jacobaea and injected Senecio alkaloids and monocrotaline on guinea pigs.

The chronic toxicity of 10% dietary Senecio jacobaea (SJ) in guinea pigs was studied during a 365-d feeding trial. The SJ plant contains hepatoxic pyrrolizidine alkaloids (PA). The chronic lethal dose (LD100) of SJ for guinea pigs was 1,264 g/kg initial body weight or 526% of initial body weight with an average survival time of 279 d. No mortality was observed in the controls. The LD100 and survival time were slightly, but not significantly, increased when 1% cysteine was included in the SJ diet. Histopathological examination of liver tissue from SJ-intoxicated guinea pigs revealed extensive megalocytosis, cytoplasmic and nuclear vacuolization, biliary hyperplasia and periportal fibrosis. Centrilobular areas appeared spared from necrotic lesions. The toxicity of acutely administered (ip) PA was determined in another experiment. The PA monocrotaline was nontoxic to guinea pigs at doses up to 1,000 mg/kg body weight, whereas jacobine and mixed SJPA were highly toxic at doses ranging from 100 to 150 mg/kg body weight. These results indicate that guinea pigs are resistant to dietary SJ and vary in response to single ip doses of isolated PA.