Partial characterization of binding sites of VA-045, a novel apovincaminic acid derivative, in rat brain membranes.
1. We characterized the binding sites of VA-045 [(+)-eburunamenine-14- carboxylic acid (2-nitroxyethyl)ester] in the rat brain. 2. VA-045 showed no affinity for various types of well-known neurotransmitter-related receptors or channels. However, radiolabeled VA-045 ([3H]VA-045) bound to rat brain membranes in a saturable and reversible manner. The Kd and Bmax values of [3H]VA-045 binding were 58.2 nM and 2685 fmol/mg of protein, respectively. 3. The largest specific binding of [3H]VA-045 was observed in the cerebellum, among seven brain regions, and in subcellular synaptosomes. 4. Specific binding of [3H]VA-045 was inhibited by VA-045 (Ki = 0.06 microM), a levorotatory enantiomer of VA-045 (VA-213) and its structural analog, vinpocentine. Moreover, compounds with calmodulin antagonistic activity inhibited the [3H]VA-045 binding. 5. These results suggest that VA-045 binds to specific sites, which may resemble calmodulin, on synaptic membranes in the brain.
Shirasaki
T
T
Taisho Pharmaceutical Co., Ltd., Saitama, Japan.
Tanaka
M
M
Muramatsu
M
M
Otomo
S
S
Kitamura
Y
Y
Nomura
Y
Y
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D008297:Male; D018377:Neurotransmitter Agents / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011955:Receptors, Drug / Q000378:metabolism*; D013574:Synaptosomes / Q000378:metabolism; D014748:Vinca Alkaloids / Q000378:metabolism*
D018377:Neurotransmitter Agents; D011955:Receptors, Drug; D014748:Vinca Alkaloids; C081044:2-(nitrooxy)ethyl apovincaminate