Active proton uptake by chromaffin granules: observation by amine distribution and phosphorus-31 nuclear magnetic resonance techniques

Abstract
The hydrogen ion activity within isolated [bovine adrenal] chromaffin granules can be estimated from the distribution of the weak base methylamine and from 31P NMR spectra of ATP contained in the granules. Following the addition of ATP to the external medium, the internal pH drops by 0.2 to 0.5 unit. This change occurs only in medium containing a permeant anion such as Cl- and is abolished by an uncoupler of oxidative phosphorylation. The chromaffin granule membrane apparently possesses an electrogenic proton pump directed inward.