Affinity of mosapride citrate, a new gastroprokinetic agent, for 5-HT4 receptors in guinea pig ileum.
We examined the binding affinity of mosapride citrate (mosapride) (4-amino-5-chloro-2-ethoxy-N-[[4-(4-fluorobenzyl)-2-morpholinyl]me thyl] benzamide citrate), a novel gastroprokinetic agent, for the 5-hydroxytryptamine (5-HT) 4 receptors in guinea pig ileum using a selective 5-HT4-receptor radioligand, [3H]GR113808. In membrane preparations from longitudinal muscle with myenteric plexus in guinea pig ileum, specific [3H]GR113808 binding revealed a single saturable site of high affinity (Kd=0.28 +/-0.02 nM, Bmax = 45+/- 3 fmol/mg protein). Mosapride and other 5-HT4-receptor agonists inhibited the specific binding of [3H]GR113808 in guinea pig ileum. The 5-HT4 agonists examined displayed the following inhibition potency order: BIMU-8 > cisapride > mosapride > renzapride > 5-HT > zacopride > metoclopramide. Mosapride exhibited monophasic inhibition of the specific [3H]GR113808 binding in the ileum (Ki value: 84.2 nM). The presence of mosapride (30 nM) significantly increased the Kd value to 0.44+/-0.05 nM in the Scatchard analysis of [3H]GR113808 binding. Bmax of [3H]GR113808, however, was not affected (48 +/-4 fmol/mg protein) by mosapride. As for the affinity of mosapride, the addition of GppNHp (100microM) slightly increased the Ki value to 104 nM. These results indicate that mosapride has an affinity for 5-HT4 receptors in guinea pig ileum in the radioligand binding study.
Yoshikawa
T
T
Discovery Research Laboratories I, Dainippon Pharmaceutical Co., Ltd., Suita, Osaka, Japan.
Yoshida
N
N
Mine
Y
Y
Hosoki
K
K
D000818:Animals; D001549:Benzamides / Q000378:metabolism*; D001667:Binding, Competitive; D018492:Dopamine Antagonists / Q000378:metabolism*; D004558:Electric Stimulation; D006168:Guinea Pigs; D007082:Ileum / Q000378:metabolism* / Q000502:physiology; D066298:In Vitro Techniques; D007211:Indoles / Q000378:metabolism; D008297:Male; D009025:Morpholines / Q000378:metabolism*; D009119:Muscle Contraction; D011869:Radioligand Assay; D011985:Receptors, Serotonin / Q000378:metabolism*; D044422:Receptors, Serotonin, 5-HT4; D012702:Serotonin Antagonists / Q000378:metabolism; D013449:Sulfonamides / Q000378:metabolism; D014316:Tritium
D001549:Benzamides; D018492:Dopamine Antagonists; D007211:Indoles; D009025:Morpholines; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D013449:Sulfonamides; D014316:Tritium; D044422:Receptors, Serotonin, 5-HT4; C062720:mosapride; C082871:GR 113808