GAMMA-AMINOBUTYRIC-ACID RADIORECEPTOR-ASSAY - A POSSIBLE BIOMARKER FOR HUMAN EXPOSURE TO CERTAIN AGROCHEMICALS

Cyclodiene insecticides, hexachlorocyclohexanes, pyrethroids, bicyclop hosphates, the bicycloorthocarboxylate insecticides and some of their metabolites and environmental degradation products are central nervous system toxicants with high specific binding affinity to the chloride channel of the gamma- aminobutyric acid (GABA)(A) receptor-ionophore s ites. [S-35] tertiary-butylbicyclophosphorothionate (TBPS) with specif ic activity higher than 60 Ci/mmole has a high binding affinity to the same sites and is now commercially available and can be used to label the. GABA(A) receptor for the development of a radioreceptor assay te chnique. The GABA receptor was prepared by ultra centrifugation and di alysis of brain homogenates of either cow, goat, rat or catfish. The r eceptor was then labeled with [S-35] TBPS and the assay was conducted by measuring the displacement of radioactivity following incubation wi th samples containing the analytes. A radioreceptor assay protocol was developed to measure the amount of the alpha-endosulfan in blood samp les. The assay was extremely sensitive, and can detect 0.2 nM of endos ulfan at a level equivalent to 0.08 ppb or 8x10(-11) gm of endosulfan in each ml of the blood samples.