Multi-xenobiotic-resistance a possible explanation for the insensitivity of bivalves towards cyanobacterial toxins

    loading  Checking for direct PDF access through Ovid


Filterfeeders, such as bivalves, are highly affected during toxic cyanobacterial blooms, as they are non-selective and may use the cyanobacteria as main nutrition source. The freshwater mussel Dreissena polymorpha, living in lakes and rivers coexisting with cyanobacteria, was exposed to 100 μg L−1 microcystin-LR (MC-LR) for up to three days. MC-LR concentration in mussel tissue and surrounding media was quantified by HPLC-PDA during uptake and depuration phase, revealing an immediate, continuous uptake, and release of non-metabolized toxin, and occurrence of reincorporation. The involvement of multi-xenobiotic-resistance protein (P-glycoprotein, P-gp) on the excretion of MC-LR was evidenced by efflux and accumulation version of the Rhodamine Assay as well as on P-gp gene expression. P-gp expression was enhanced after 1 h exposure but no changes were detected after longer (72 h) exposure. P-gp enzyme activity showed a significant increase with exposure time, supporting the hypothesis that P-gp is involved in the excretion of MC-LR.

Induction of biotransformation enzyme such as pi-class glutathione S-transferase (piGST) and antioxidant enzyme catalase (CAT) was immediately inhibited and returned to control values only after more than 72 h expose time. Heat shock protein 70 (hsp70) and protein phosphatase 2A (PP2A) gene expression was not changed due to the treatment with cyanobacterial toxin MC-LR.

Related Topics

    loading  Loading Related Articles