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Multiple [ 35 S] t ‐Butylbicyclophosphorothionate Binding Sites in Rat and Chicken Cerebral Hemispheres
Author(s) -
Tehrani Mohammad H. Jalilian,
Clancey Constance J.,
Barnes Eugene M.
Publication year - 1985
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1985.tb05560.x
Subject(s) - cerebrum , radioligand , dissociation constant , binding site , chemistry , scatchard plot , stereochemistry , biophysics , endocrinology , biology , receptor , biochemistry , central nervous system
Specific binding of [ 35 S] t ‐butylbicyclophosphorothionate (TBPS) to membranes from cerebral hemispheres of adult rat and chicken was determined over a range of radioligand concentrations from 0.25 to 500 n M. Scatchard plots of these data were curvilinear and non‐linear regression analysis indicated binding to two sites that differ in affinity. For rat cerebrum, K D(1) = 1.15 n M , B max(1) 0.085 pmol/mg; K D(2) = 232 n M, B max(2) = 16.9 pmol/mg. For chicken cerebrum, K D(1) = 1.39 n M, B max(1) = 0.111 pmol/mg; K D(2) = 166 n M, B max(2) = 17.6 pmol/mg. This multiplicity of [ 35 S]TBPS binding was further confirmed when unlabeled TBPS or picrotoxinin displaced radioligand. The displacement curves were biphasic and yielded Hill coefficients from 0.65 to 0.70. These displacement curves were also resolved into two components with distinct IC 50 values for unlabeled TBPS (rat, 1.55 and 271 n M ; chicken, 2.40 and 224 n M ). The IC 50 values were similar to the dissociation constants obtained from equilibrium binding measurements.