EFFECT OF RAPID INTRAATRIAL SALINE INFUSION ON ATRIAL PRESSURES AND ATRIAL NATRIURETIC HORMONE-SECRETION

To evaluate the relationship between the right atrial pressure and atr ial natriuretic hormone secretion, we studied 16 healthy mates, ages 1 8-24, after five days on a low-salt diet (mean 24-h urinary sodium exc retion: 17 +/- 3 mEq). After 90 min of equilibration to the supine pos ition, a multilumen catheter was inserted into the right atrium, and 1 I of isotonic saline was infused intra-atrially over 15 min through th is catheter. Blood pressure, heart rate, and right atrial pressure wer e recorded just before (0 min), immediately after completion of the in fusion (15 min), and every 15 min for 45 min thereafter. Two blood sam ples were drawn at each time point for atrial natriuretic hormone assa y: one from the right atrium (central) and the other from a peripheral vein. Blood pressure did not change significantly during the entire s tudy. Heart rate increased by 5 beats/min on average at 15 min (p < 0. 005) and returned to baseline at 60 min. Good correlation occurred bet ween central and peripheral atrial natriuretic hormone levels at times 0, 30, 45 and 60 min (r(2) = 0.,66, 0.45, 0.76 and 0.70, respectively ; p less than or equal to 0.02). An increase in right atrial pressure and an increase in central atrial natriuretic hormone levels correlate d well at times 30, 45 and 60 min, but there was no such correlation b etween an increase in right atrial pressure and an increase in periphe ral atrial natriuretic hormone levels at any time point. Similarly, a maximum increase in right atrial pressure correlated with a maximum in crease in central atrial natriuretic hormone levels (r(2) = 0.48; p < 0.02), but not with a maximum increase in peripheral levels of this ho rmone. We concluded that an increase in right atrial pressure caused b y a rapid infusion of isotonic saline induces secretion of atrial natr iuretic hormone in the right atrium. The observed discrepant course of change in central and peripheral atrial natriuretic hormone levels su ggests the additional contribution of secretion beyond the level of th e coronary sinus.