In vivo and in vitro intestinal transport of 3H-microcystin-LR, a cyanobacterial toxin, in rainbow trout (Oncorhynchus mykiss)

The intestinal uptake of the tritiated form of the cyanobacterial hepatotoxin microcystin-LR (MC-LR) by rainbow trout (Oncorhynchus mykiss) was investigated in vivo and in vitro. Rainbow trout were administered a single dose of 1 mM H-3-MC-LR by oral gavaging. After 24 h, approximately 0.3% of the radiolabel delivered into the intestine was detected in the liver and muscle, but not the spleen or kidney. The distribution of radiolabel in these tissues was not affected by 10 mM of the bile salt deoxycholate or 1 mM of 'cold' MC-LR. The in vitro intestinal transport of MC-LR from mu-osa to serosa was linear with respect to intestinal concentrations of MC-LR over a range of 1.6 mu M and 101 mM, and was not affected by the Na+/K+-ATPase inhibitor cuabain, suggesting that a component of MC-LR transport across the intestine of rainbow trout may be passive. (C) 1998 Elsevier Science B.V. All rights reserved.