Toxicity of Echium plantagineum (Paterson's Curse). 2. Pyrrolizidine alkaloid poisoning in rats

Abstract

Food pellets containing Echium plantagineum were incorporated into the diet of adult and weanling rats to provide either a 20 or a 40% level of Echium. These diets were fed, either continuously or intermittently, for 14 to 280 days. A high mortality from acute or chronic pyrrolizidine alkaloid poisoning occurred in all groups given Echium. Young rats fed on 20-40% Echium for up to 28 days had a 70% mortality from acute haemorrhagic necrosis of the liver between days 22 and 35. Rats that received Echium continuously or intermittently over extended periods died with a mixture of acute necrosis and chronic liver damage typical of pyrrolizidine alkaloid poisoning. Young rats fed on 40% Echium for only the first 14 days, and having consumed no more than 0.7 g total alkaloid per kg liveweight, developed extensive chronic liver damage, leading to deaths from the 35th day after the start of feeding. The activity of liver microsomes in the production of pyrrolic metabolites from Echium alkaloids was 5-7 times greater in rats than in sheep. These results are discussed in relation to the relatively very low susceptibility of sheep to ingested Echium alkaloids.