ATRIAL-NATRIURETIC-FACTOR DOES NOT AFFECT NOREPINEPHRINE CATABOLISM IN RAT HYPOTHALAMUS AND ADRENAL-MEDULLA

We have previously reported that atrial natriuretic factor (ANF) incre ases neuronal uptake and endogenous content of norepinephrine (NE) and diminishes neuronal release, synthesis and turn-over of NE in rat hyp othalamus and adrenal medulla. The aim of the present work was to stud y another aspect of NE metabolism and therefore investigate the possib le effects of ANF on NE catabolism. The determination of monoamine oxi dase (MAO) and catechol-O-methyl transferase (COMT) activity and deami nates metabolites formation were studied in vitro in rat hypothalamus and adrenal medulla slices. Results showed that, in the hypothalamus, 100 nM ANF diminished MAO activity while 10 nM ANF did not modify the enzyme activity. Conversely, 10 and 100 nM ANF reduced MAO activity in adrenal medulla. On the other hand, the atrial factor modified neithe r COMT activity nor the formation of deaminates metabolites in the hyp othalamus and adrenal medulla. Present results as well as previous fin dings support a putative role for ANF in the modulation of NE metaboli sm not only in the hypothalamus but also in the adrenal medulla of the rat, affecting the storage, release and uptake of NE but not its cata bolism. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.