Biochemical Studies on Oral Toxicity of Ricin. IV. A Fate of Orally Administered Ricin in Rats

Abstract

After oral administration of ricin in rats, its distribution in the gastrointestinal tract, body fluids and principal organs was determined by an enzyme im munoassay, and the immunoreactive ricin detected was identified by gel filtration followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, protein blo tting and the immunobinding method. When ricin D (10 mg/kg rat) was given orally to a rat, which dose is equivalent to 1/3 LD50, about 75% of the ricin was found in the stomach and small intestine within 2 h, and most of it was transferred to the large intestine after 24 h. It was also demonstrated by an in vitro toxicity test of immunoreactive ricin in the blood and lymph obtained from the intoxicated rats that a part of the ricin was absorbed from the small intestine into the tissues a nd organs via the circulatory systems (lymphatic and blood vessels) as the active ricin. The participation of the blood vessels was greater in the absorption of ric in from the gastrointestinal tract than that of the lymphatic system. Ricin, after absorption, was detected in liver and spleen and ricin found in the liver was pre dominantly in the form of intact ricin, although an undetectable amount of ricin in other organs cannot be eliminated. These results infer that a small fraction of orally-given ricin was transferred to the circulating system and was responsible for rat's death as in the case of i.p. administration. © 1992, The Pharmaceutical Society of Japan. All rights reserved.