Disposition of rubratoxin B in the rat

Excretion, tissue concentrations in the kidney and liver, and pharmacokinetic parameters estimated from plasma blood concentrations were determined for rats given a single ip dose of [¹⁴C]rubratoxin B (0.05 mg dissolved in propylene glycol). By 7 days, 80% of the administered radioactivity had been excreted into the urine (41.7%) and feces (38.7%). Urinary excretion was primarily as the parent compound, accounting for 75% of the radioactivity excreted by 7 days. Elimination of radio-activity from the kidneys was monophasic with a half-life of 97.35 hr. Elimination of radioactivity from the liver was biphasic, with a half-life of 13.66 hr for the slow phase. Elimination of rubratoxin B and [¹⁴C]rubratoxin B-derived radioactivity (radioactivity derived from both the parent compound and metabolites) from the plasma was biphasic. The rapid phases of elimination had half-lives of 2.57 and 1.08 hr, and the slow phases had half-lives of 60.80 and 100.46 hr for rubratoxin B and [¹⁴C]rubratoxin B-derived radio-activity respectively. The long plasma half-life of rubratoxin B is suggestive of enterohepatic circulation. The concentration of radioactivity was greatest at 1 hr in the liver and 2 hr in the plasma. Except for the first few hours following injection, the concentration of radioactivity in the liver never exceeded significantly that in the plasma, suggesting a passive absorption process. No glucuronide or sulfate conjugates were detected in the plasma or urine.