Analysis of paralytic shellfish poisoning toxin congeners by a sodium channel receptor binding assay

• Published in: Toxicon (Oxford) 2004-07, Vol.44 (1), p.37-43
• Main Authors: Usup, Gires, Leaw, Chui-Pin, Cheah, Mei-Yee, Ahmad, Asmat, Ng, Boon-Koon
• Format: Article
• Language: English
• Subjects: Animals; Binding, Competitive; Biological and medical sciences; Biological Assay - methods; Brain - metabolism; Dinoflagellida - chemistry; Male; Marine Toxins - metabolism; Medical sciences; Paralytic shellfish poisoning; Paralytic shellfish poisoning toxin detection; Plant poisons toxicology; Rats; Rats, Sprague-Dawley; Rattus; Receptor binding assay; Shiga Toxin - metabolism; Sodium channel; Sodium Channels - metabolism; Toxicology; Tritium
• ISSN: 0041-0101; 1879-3150
• DOI: 10.1016/j.toxicon.2004.03.026

This study was carried out to characterize the detection and quantitation of several paralytic shellfish poisoning (PSP) toxin congeners using a receptor binding assay (RBA). This involved competitive binding of the toxin congeners against tritium-labeled STX for receptor sites on rat brain sodium channels. Competitive binding curves were described by a four-parameter logistic equation. Half-saturation values (EC 50) ranged from 4.38 nM for STX to 142 nM for GTX5. Receptor binding affinity was in the order STX>GTX1/4>neoSTX>GTX2/3>dcSTX>GTX5, and this was similar to the order of mouse toxicity of these congeners. Predicted toxin concentrations from observed STXeq values and EC 50 ratios relative to STX were within 20% or better of the actual concentrations used in the assay. In contrast predicted toxin concentrations using mouse toxicity ratios relative to STX did not provide a good match to actual concentrations, except for GTX1/4. This study has shown that the rat brain sodium channel RBA will provide a reliable integration of total toxicity of various PSP toxin congeners present in a sample.