HISTOCHEMICAL STUDIES ON UPTAKE OF NORADRENALINE AND ALPHA-METHYL-NORADRENALINE IN PERFUSED RAT HEART

The cellular localization of noradrenaline and α-methyl-noradrenaline taken up by the rat isolated heart during perfusion was studied. After perfusion with low concentrations, 0.02-0.2 μg/ml, uptake of the catecholamines into the adrenergic nerves occurred but no evidence for an extraneuronal uptake was found. After perfusion with high concentrations, 5-20 μg/ml, there was a markedly increased flourescencein the heart muscle cells. In the atria numerous small intensely fluorescent connective tissue cells could be found. In both cases the fluorescence proved to be due to the presence of catecholamines. The extraneuronal uptake could be inhibited by normetanephrine but not desipramine. It is concluded that the catecholamines taken up in the rat heart during perfusion with high concentrations are located partly in the adrenenic nerves but also to a great extent extraneuronally. © 1969.