POSSIBLE MECHANISMS INVOLVED IN THE NATRIURETIC RESPONSE TO ATRIAL-NATRIURETIC-FACTOR (ANF) AND PROANF-31-67 IN THE RAT

1. The present study was conducted to compare the mechanisms involved in the natriuretic response to atrial natriuretic factor (ANF) and pro ANF 31-67. The peptides were infused intravenously into anaesthetized rats at 10 pmol/min for 40 min. 2. Only ANF produced a significant dec rease in arterial pressure; the maximum decrease was 11 mmHg (P<0.05). 3. Both peptides produced significant increases in sodium excretion ( P<0.05) but only ANF increased the cyclic GMP (cGMP) excretion rate (P <0.01) and neither peptide had a significant effect on plasma renin ac tivity or glomerular filtration rate (GFR). ProANF 31-67 did not incre ase the plasma levels of ANF. 4. These results demonstrate that both A NF and proANF 31-67 have natriuretic effects via a tubular mechanism a nd suggest that the natriuretic effects of ANF are mediated by cGMP wh ile the effects of proANF 31-67 are mediated by a different mechanism, not involving changes in cGMP excretion, changes in GFR or a reductio n in renin secretion.