EXTRANEURONAL UPTAKE OF NORADRENALINE IN HUMAN TISSUE (UPTAKE(2))

The neurotransmitter, noradrenaline, is inactivated by active transpor t out of the synaptic cleft, either back into the adrenergic neurons ( uptake(1)) or into extraneuronal cells (uptake(2)). Although experimen tal models clearly demonstrate uptake(2) in various animal tissues, th ere are few reports of studies that demonstrate uptake(2) in human tis sue. Furthermore, uptake(2) has never been described in human heart ti ssue. We demonstrated a reduction of H-3-noradrenaline uptake in human atrial and venous tissue and in rat atrial and Ventricular tissue by O-methylisoprenaline - a known inhibitor of uptake(2.) These results i ndicate that uptake(2), as has been described in previous experimental models, does exist in humans and further, the results emphasize the i mportance of uptake(2), since about 50% of exogenous noradrenaline is inactivated by uptake(2) in the rat heart.