Specific high-affinity binding of L-[3H]aspartate to rat brain membranes.
The binding of L-[3H]aspartate was investigated in washed membranes prepared from whole rat brain. We were able to differentiate two separate binding sites differing in their Na dependence. The Na-independent binding was saturable, reversible, and optimal at 20 degrees C and at pHs in the neutral range. The dissociation constant (Kd) at 20 degrees C was about 200 nM. This binding site seemed to be modulated by magnesium and calcium at physiological concentrations. None of the amino acids tested was a potent competitor for Na-independent L-[3H]aspartate binding. This binding site was unevenly distributed in the rat central nervous system: cerebellum = cerebral cortex greater than pons-medulla greater than spinal cord. Destruction of the intrinsic neurons of the cerebellum by injecting kainic acid 30 days before sacrifice resulted in a 53% reduction in Na-independent binding in this region. The Na-dependent binding of L-[3H]-aspartate (Kd = 4894 nM) was strongly inhibited by D-aspartate, L-glutamate, D,L-aspartate beta-hydroxamate; was unaffected by calcium and magnesium; and showed a different pattern of distribution: cerebral cortex greater than cerebellum = pons-medulla = spinal cord. This binding in cerebellum was unaffected by injections of kainic acid.
D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D001665:Binding Sites; D001921:Brain / Q000378:metabolism*; D002413:Cations, Divalent / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D007608:Kainic Acid / Q000378:metabolism; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D013997:Time Factors
D002413:Cations, Divalent; D001224:Aspartic Acid; D012964:Sodium; D007608:Kainic Acid