Specific inhibition of endogenous shellfish protein phosphatase that couldbe used as a direct reporter of Diarrhetic Shellfish Poison

Diarrhetic Shellfish poisoning (DSP) is a human gastrointestinal disorder a ssociated with the consumption of contaminated sliellfish. Okadaic acid (OA ) and dinophysisroxin-1 (DTX-1) are diarrogenic DSP toxins, which also have tumor promotion and protein phosphatase inhibition activities. It is also known that OA and DTX-1 toxins localize mainly in the shellfish digestive g land; although, it remains to be explained how the toxins are retained in t his tissue. Total protein of shellfish digestive gland from different shell fish species was fractionated using gel electrophoresis under nondenaturing conditions followed by specific phosphatase colored reaction. This Procedu re allows the identification of endogenous shellfish protein phosphatases t hat are shellfish species specific. Moreover, when shellfish digestive glan ds naturally contaminated by DSP were evaluated using the same procedure, o ne or both of previously identified endogenous protein phosphatase acitivit ies showed reduction or inhibition as compared to uncontaminated controls. To demonstrate experimentally that the protein phosphatase inhibiton observ ed were attributable to DSP toxins, shellfish of Venus antiqua were toxifie d using Prorocentrum lima cells under laboratory conditions, and their dige stive glands were analyzed as described above, The same protein phosphatase inhibition was detected in shellfish naturally contaminated with DSP. Thes e observations suggest that endogenous shellfish protein phosphatases could act as acceptors for DSP toxins, and their analysis can be used as a simpl e and sensitive assay to detect DSP toxins in shellfish, avoiding DSP purif ication steps, and reducing the time for DSP detection and animal use.