The aim of this paper is to establish the relative intraperitoneal toxicity of dinophysistoxin-2 (DTX-2) compared with okadaic acid (OA). The study was performed as an open, randomised parallel group trial with a four level response surface design within each of the two parallels.
In accordance with the response surface design model, the LD50 for DTX-2 and OA was 338 and 206 μg/kg, respectively. By use of common regression analysis, the LD50 of DTX-2 and OA were estimated to 352μg/kg and 204μg/kg, respectively. The deviations between the LD50 estimates by the two methods was 4%for DTX-2 and less than 1%for OA. Taken together, these results indicate that the relative toxicity of DTX-2 is about 0.6, compared to OA.
Results from the PP2A assay correspond very well with the results obtained by the mouse bioassay. The IC50 concentrations for DTX-2 and OA were 5.94 and 2.81 ng/mL, respectively. This indicates that OA is about twice as toxic as DTX-2. Since inhibition of PP2A is acknowledged as the main mechanism of toxicity of the OA group toxins, this supports the establishment of a relative toxicity factor of DTX-2 of 0.6 compared with OA.