Regulatory acceptance, tissue

The accepted mouse bioassay for domoic acid is based on the AOAC bioassay for saxitoxin (PSP). In brief, shellfish tissue is boiled in O.IN HCl, cooled and pH adjusted, and injected intraperi-toneally (i.p.) in serial dilutions. Time- and dose-dependent toxicity symptoms are recorded for 4 h and used to determine concentration in the sample by interpolation from standard curves. The limit of sensitivity of the assay is considered to be 40 ppm, which is double the regulatory limit in most countries [47], although reproducible behavioral change can be detected at much lower concentrations [48] in controlled laboratory conditions. 

The principal regulatory method to protect consumers from marine toxins in food is the mouse bioassay. It measures the time to death after intraperitoneal injection of a toxic extract, and toxicity is expressed as the amount of toxin (usually in micrograms) or toxin equivalents (eq) per gram (or 100 g) of shellfish tissue, standardized against a reference toxin solution. As it is a reliable indicator of human oral toxicity, the mouse bioassay is obligatory prior to commercialization of seafood in many countries. However, this biological test does not allow for specification of toxins or studies on the formation and effect of individual toxins. In addition, it has a high variability ( 20%) and low sensitivity, lacks specificity, and often has detection limits too near to the accepted threshold. Yet, the major limitation of the mouse bioassay is of ethical and political nature due to the use of live animals. 

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