The neuronal transport mechanism for noradrenaline is not influenced by the ATP analogue ATP gamma S.

Noradrenaline is taken up in noradrenergic neurones via a desipramine-sensitive transport system (uptake1). There are reports which describe the activity of uptake1 being increased by extracellular ATP and ATP gamma S. This was attributed to a protein kinase-mediated mechanism. We reevaluated this phenomenon since a modulation of uptake1 by extracellular ATP would be of great physiological relevance. In clonal rat pheochromocytoma cells (PC12) we determined the kinetic parameters, Km and Vmax, of noradrenaline transport in the absence and presence of ATP gamma S. The addition of 0.1 mumol/L ATP gamma S had no effect on initial rates of specific noradrenaline transport. Only a slightly increased non-specific noradrenaline flux in the presence of ATP gamma S could be observed. On the basis of our results, there is no evidence for the modulation of the uptake1 carrier by ATP gamma S.