Real-time measurements of acetylcholine-induced release of ATP from bovine medullary chromaffin cells

The luminescent oxidation of luciferin has been used to monitor acetylcholine-induced ATP release from cultured bovine chromaffin cells. Acetylcholine (1-100 μM) evoked ATP release of up to 30% of the total cellular ATP. This secretion required external free calcium and could also be elicited by K+-induced membrane depolarization. The size of the cytosolic ATP compartment was estimated as 5% of the ATP in the cell by solubilising the cell membrane using digitonin (20 μM) or by application to the cells of brief pulses (2 μs) of high electric field (2000 V cm). Blockers of the voltage-gated Ca²⁺ channel effectively blocked K⁺-induced ATP release, while the acetylcholine antagonists d-tubocurarine and β-bungarotoxin inhibited the acetylcholine-induced release of ATP. These data support the concept that ATP is released together with the catecholamines by exocytosis of chromaffin granule contents. ATP secretion Chromaffin cell Acetylcholine channel Exocytosis Catecholamine.