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Variability Of Microcystin-LR Standards Available From Commercial Vendors
Citation:
Hill, D., N. Chernoff, J. Lang, Thanh-Thao Le, AND Judy Schmid. Variability Of Microcystin-LR Standards Available From Commercial Vendors. To be Presented at US Harmful Algae Symposium, Baltimore, MD, November 12 - 17, 2017.
Impact/Purpose:
To demonstrate variability in mass and purity of microcystin-LR standards purchased from different vendors and why this has significant analytical and toxicological consequences. This would be important to algal and cyanotoxin researchers and suppliers, and would impact quality of data and reproducibility of research using these standards. Without awareness of this variability and the need to confirm purity and mass with analytical chemistry, interpretation of inaccurate data could affect measurements necessary to enforce or substantiate water exposure guidelines.
Description:
Microcystins are the most common group of cyanobacterial hepatotoxins found in freshwater in the U.S., and microcystin-LR (MCLR) is one of the most common forms. Understanding its spectrum of effects and dose-response relationships depends on consistent experimental results which are dependent on the accuracy of toxin quantities used in toxicology studies. Our laboratory experienced significant differences in MCLR toxicity after administration to mice at similar doses based on label information of standards from two vendors. MCLR was purchased from seven vendors to test for source variability, and doses of 40µg/kg were administered intraperitoneally to mice based on the quantity information supplied with the toxin. The extent of inter-vendor variability was measured by examination of animals for gross toxicity, organ weights, serum clinical chemistry endpoints, histopathology, and gene expression. The toxicity endpoints remained similar across vendors, but the extent of the toxicity varied significantly ranging from massive liver damage to only small changes in liver serum markers. Analyses of these toxins (reported in a separate presentation at this Meeting) indicated that MCLR was present in all vendor samples, but the quantities varied significantly. Our laboratory’s combined results indicated significant correlation between actual quantities and the magnitude of toxic responses. We suggest that toxicology studies involving extracted biotoxins such as cyanotoxins, should be preceded by analysis of the study compounds to ensure that any effects noted are accurate reflections of the amounts of toxins used in the exposures.