Receptors on the neutrophil membrane. I. Flunarizine-adenosine antagonism as detected by 1H-nuclear magnetic resonance relaxation investigations.

Selective proton relaxation rates were measured for selected protons of flunarizine in the presence of neutrophils, yielding evidence of a binding interaction that involves different moieties of the drug. Fast exchange between bound and free environments was demonstrated as the main factor determining the selective relaxation rate enhancement, whereas viscosity effects were shown to be negligible. The relaxation effect was cancelled out by the presence of adenosine as a cosolute in a dose-dependent fashion, leading to the suggestion that the endogenous mediator adenosine affects binding of flunarizine to the neutrophil surface.