INFLUENCE OF ATRIAL-NATRIURETIC-FACTOR ON UPTAKE, INTRACELLULAR-DISTRIBUTION, AND RELEASE OF NOREPINEPHRINE IN RAT ADRENAL-MEDULLA

Several studies have demonstrated that atrial natriuretic factor can b ind to adrenal medulla cells. Furthermore, atrial natriuretic factor i mmunoreactivity has been identified in chromaffin cells. The aim of th e present work was to investigate atrial natriuretic factor effects on the uptake, intracellular distribution, and release of norepinephrine in the rat adrenal medulla. Results showed that 100 nM atrial natriur etic factor induced a rapid increase of norepinephrine uptake during t he first minute of the incubation period. This increase was maintained for up to 60 min. In addition, only neuronal norepinephrine uptake wa s increased by the natriuretic factor; non-neuronal norepinephrine upt ake was unaltered. Atrial natriuretic factor modified the intracellula r distribution of the amine store: the granular fraction of norepineph rine increased, while the cytosolic fraction decreased. On the other h and, different concentrations (10, 50, and 100 nM) of the atrial facto r decreased spontaneous [H-3]norepinephrine output in a concentration- dependent manner. Furthermore, atrial natriuretic factor (10 nM) also reduced high potassium solution evoked secretion of norepineprhine. Th ese results suggest that atrial natriuretic factor modulates sympathet ic activity in the rat adrenal medulla. These effects of atrial natriu retic factor may be related to the catecholamine peripheral mechanism involved in the regulation of arterial blood pressure, smooth muscle t one, metabolic activity, etc.