Adenine nucleotide and phosphoenolpyruvate transport by bovine chromaffin granule "ghosts"

Abstract

Purified bovine adrenal chromaffin granule "ghosts" (resealed membranes) accumulate nucleotides and phosphoenolpyruvate in a temperature-dependent process. Equilibration takes several hours, the compounds being accumulated to not more than twice their concentration in the medium. This uptake occurs primarily by a non-saturable diffusion process, and rates and extents show little dependence on membrane energization. Uptake rates are inhibited less than 50% by compounds that discharge the "ghost" membrane potential, or by atractylate or low concentrations of Cibacron Blue. The data gave little support to the theory that chromaffin granules have a membrane potential-dependent adenine nucleotide transport process and that nucleotides are in equilibrium with the positive-inside potential across the granule membrane.