Investigation of calcium antagonist-L-type calcium channel interactions by a vascular smooth muscle cell membrane chromatography method.
The dissociation equilibrium constant (K(D)) is an important affinity parameter for studying drug-receptor interactions. A vascular smooth muscle (VSM) cell membrane chromatography (CMC) method was developed for determination of the K(D) values for calcium antagonist-L-type calcium channel (L-CC) interactions. VSM cells, by means of primary culture with rat thoracic aortas, were used for preparation of the cell membrane stationary phase in the VSM/CMC model. All measurements were performed with spectrophotometric detection (237 nm) at 37 degrees C. The K(D) values obtained using frontal analysis were 3.36 x 10(-6) M for nifedipine, 1.34 x 10(-6) M for nimodipine, 6.83 x 10(-7) M for nitrendipine, 1.23 x 10(-7) M for nicardipine, 1.09 x 10(-7) M for amlodipine, and 8.51 x 10(-8) M for verapamil. This affinity rank order obtained from the VSM/CMC method had a strong positive correlation with that obtained from radioligand binding assay. The location of the binding region was examined by displacement experiments using nitrendipine as a mobile-phase additive. It was found that verapamil occupied a class of binding sites on L-CCs different from those occupied by nitrendipine. In addition, nicardipine, amlodipine, and nitrendipine had direct competition at a single common binding site. The studies showed that CMC can be applied to the investigation of drug-receptor interactions.
Du
Hui
H
Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education, School of Medicine, Xi'an Jiaotong University, Xi'an, 710061, China.
He
Jianyu
J
Wang
Sicen
S
He
Langchong
L
D000818:Animals; D001665:Binding Sites; D002121:Calcium Channel Blockers / Q000737:chemistry*; D020746:Calcium Channels, L-Type / Q000737:chemistry*; D002462:Cell Membrane / Q000737:chemistry*; D002478:Cells, Cultured; D002845:Chromatography / Q000379:methods*; D007700:Kinetics; D009131:Muscle, Smooth, Vascular / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type