RESERPINE BINDING TO BOVINE CHROMAFFIN GRANULE MEMBRANES - CHARACTERIZATION AND COMPARISON WITH DIHYDROTETRABENAZINE BINDING

Google Scholar
  • 1 January 1984
    • journal article
    • research article
    • Vol. 25  (1) , 113-122
Abstract
[3H]Reserpine bound reversibly in vitro to chromaffin granule membranes. Binding was temperature-dependent and slow, and had biphasic kinetics. The addition of ATP accelerated the kinetics, which became monophasic and comparable to those of [3H] dihydrotetrabenazine, without affecting the binding equilibrium constants. The ATP effect was related to H+-electrochemical gradient generation by the granule membrane H+ pump. Binding of reserpine to chromaffin granule membranes occurred on 2 classes of sites: R1, Bmax [maximum binding] = 7 pmol/mg of protein and Kd = 0.7 nM, and R2, Bmax = 60 pmol/mg of protein and Kd = 25 nM. Sites R2 were considered to be equivalent to [3H] dihydrotetrabenazine binding sites, as the densities of the R2 and the [3H]dihydrotetrabenazine binding sites were similar and because tetrabenazine displaced reserpine from R2 sites. Sites R1 were tetrabenazine-resistant; they were involved in monoamine uptake, since their Kd values were similar to the KI [inhibition constant] values of reserpine for noradrenaline [norepinephrine] uptake. Sites R1 were less abundant than sites R2 on chromaffin granule membranes, but they were present at the same concentration in intact chromaffin granules. The monoamine carrier evidently exists in 2 forms: an active form bearing both high- and low-affinity sites for reserpine and an inactive form with only the low-affinity R2 sites.