Solubilization of novel binding sites for [3H]glutamate in rat adrenal.

[3H]Glutamate binding sites were solubilized from the rat adrenal glands by treatment of the membranous homogenate preparations with various detergents. The binding in solubilized preparations was dependent on the incubation temperature and incubation time, and reached an equilibrium within 40 min of incubation at 30 degrees C. Scatchard analysis revealed that the binding sites consisted of a single component with a Kd of 0.15 microM and a Bmax of 35.9 pmoles/mg protein, respectively. The binding was significantly displaced by L-isomers of the structure-related compounds, but not by D-isomers. Quisqualic acid exhibited a concentration-dependent inhibition of the binding, whereas neither N-methyl-D-aspartic acid nor kainic acid elicited such a prominent diminution. These results suggest that the rat adrenal indeed contains novel binding sites for the central neurotransmitter candidate.