D-Aspartate binding sites in rat Harderian gland.
Radioligand binding of D-[(3)H]aspartic and L-[(3)H]glutamic acids to plasma membranes from rat Harderian gland was evaluated. Binding was optimal under physiological conditions of pH and temperature, and equilibrium was reached within 50 min. Specific binding for D-Asp and L-Glu was saturable, and Eadie-Hofstee analysis revealed interaction with a single population of binding sites (for D-Asp K(d) = 860 +/- 28 nM, B(max) = 27.2 +/- 0.5 pmol/mg protein; for L-Glu, K(d) = 580 +/- 15 nM and B(max) = 51.3 +/- 0.8 pmol/mg protein). L-[(3)H]glutamate had higher affinity and a greater percentage of specific binding than did D-[(3)H]aspartate. The pharmacological binding specificity of L-[(3)H]glutamate indicated an interaction with NMDA-type receptors. Specifically, the order of potency of the displacing compound tested was L-Glu > D-Asp > NMDA > MK801 > D-AP5 > glycine. For D-[(3)H]aspartate, the data revealed an interaction of D: -Asp with either NMDA-type receptors or putative specific binding sites.
Di Giovanni
Marcello
M
Dipartimento Scienze della Vita, Seconda Università degli Studi di Napoli, Via Vivaldi 43, Caserta, Italy. marcello.digiovanni@unina2.it
Topo
Enza
E
Santillo
Alessandra
A
D'Aniello
Antimo
A
Chieffi Baccari
Gabriella
G
D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D006243:Harderian Gland / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D011485:Protein Binding; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism
D016194:Receptors, N-Methyl-D-Aspartate; D001224:Aspartic Acid