Toxicokinetics of Microcystin and Dihydro-Microcystin in Swine

Abstract : Tritiated dihydromicrocystin-LR ((3H)2H-MCLR) plus 2H-MCLR were given to anesthetized pigs IV or via an ileal loop. over half the radiolabel in blood at one minute after dosing IV was cleared by 6 minutes; clearance at 25 micrograms/kg was faster than at 75 micrograms/kg. At 75 micrograms/kg via the ileum, the blood concentration peaked at 90 minutes, and the concentration in portal blood was 3.6 times greater than in peripheral blood. Radioactivity was first detected in bile at 12 minutes post-dosing. At 4 hours after dosing IV at 25 or 75 ug/kg, and at 5 hours after dosing via the ileal loop at 75 micrograms/ kg, radiolabel was distributed as follows: liver (64.6, 46.99, and 49.5 percent of total dose %TD), kidneys (1.2, 2.19, and 1.04 %TD), lungs (1.75, 0.55, and 0. 65 %TD), heart (0.22, 0.23, and 0.81 %TD), ileum (0.13, 0.20, and 33.94 %TD), and spleen (0.04, 0.07, and 0.16% %TD), respectively. Most hepatic radiolabel was attributable to parent compound, although two minor radioactive components were isolated. Previous evidence indicating inhibition of protein phosphatases by intact microcystins and the observation that nearly all 3H 2H-MCLR in the liver was parent compound during lesion development suggest that microcystins are toxicologically active in vivo as parent compounds. Microcystin, Blue-green algae, Cyanobacteria, Toxin, Liver, Fate, Toxicokinetics, Pharmacokinetics, Lesions, Toxicity.