F. Graziani et al., INTERACTION OF LACIDIPINE WITH ITS RECEPTOR-BINDING SITE SUPPORTS A SLOW ONSET AND LONG-DURATION OF ACTION, Journal of cardiovascular pharmacology, 27(2), 1996, pp. 290-296
[H-3]lacidipine binding to its receptor was characterized to explain i
ts slow onset and long duration of antihypertensive activity. Binding
parameters were studied in guinea pig myocardial and cerebral membrane
preparations and compared with another dihydropyridine (DHP) calcium
antagonist, isradipine. Lacidipine binds competitively to the DHP calc
ium antagonist receptor of the L-type calcium channel. The binding is
allosterically modulated by verapamil and D-cis diltiazem and activate
d/inhibited by divalent cations. Association and dissociation kinetics
of the binding of lacidipine to the receptor were significantly slowe
r than those of isradipine. In addition, the B-max of lacidipine bindi
ng in guinea pig heart microsomes was significantly higher than those
of other dihydropyridine calcium antagonist. The results indicate that
the slow onset and long duration of action of lacidipine can be expla
ined principally on the basis of the binding characteristics. Although
no biphasic receptor binding kinetics could be detected, a fast equil
ibrium between the receptor and a second compartment, due to the high
lipophilicity of lacidipine, cannot be excluded.