title: Analysis of paralytic shellfish poisoning toxin congeners by a sodium channel receptor binding assay.
abstract: 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.
authors.affiliation: Marine Science Programme, Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia. gires@ukm.my
authors.forename: Gires
authors.initials: G
authors.lastname: Usup
authors.forename: Chui-Pin
authors.initials: CP
authors.lastname: Leaw
authors.forename: Mei-Yee
authors.initials: MY
authors.lastname: Cheah
authors.forename: Asmat
authors.initials: A
authors.lastname: Ahmad
authors.forename: Boon-Koon
authors.initials: BK
authors.lastname: Ng
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001681:Biological Assay / Q000379:methods*; D001921:Brain / Q000378:metabolism*; D004141:Dinoflagellida / Q000737:chemistry*; D008297:Male; D008387:Marine Toxins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D022621:Shiga Toxin / Q000378:metabolism; D015222:Sodium Channels / Q000378:metabolism*; D014316:Tritium
chemical_list: D008387:Marine Toxins; D015222:Sodium Channels; D014316:Tritium; D022621:Shiga Toxin