Disposition of the toxic protein, bolesatine, in rats: its resistance to proteolytic enzymes.

1. Bolesatine is a toxic protein (LD50 oral 3.3 mg/kg in mice) isolated from the mushroom Boletus satanas Lenz, which inhibits protein synthesis in vitro. It induces gastroenteritis in human. 2. 14C-Bolesatine, given orally to rats (30 micrograms/kg), is distributed in the gastrointestinal, tract, kidney, liver and, to a lesser extent, in the thymus, spleen and lung. Bolesatine is eliminated in faeces and urine (80% in 24h). 3. The material excreted in urine is not proteolysed, and no protease (trypsin, chymotrypsin, pronase, proteinase K, Staphylococcus aureus (strain V8) protease and pepsin) is found to hydrolyse bolesatine in either its native or denatured form. However, thermolysin hydrolysed denatured bolesatine to a protein having a Mr of about 55 kD. 4. Bolesatine is found in all the following rat liver and kidney subcellular fractions: cytoplasm, mitochondria, ribosomes, microsomes and nuclei.