The Role of Frequency of Atrial ContractionVersusAtrial Pressure in Atrial Natriuretic Peptide Release*

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Abstract
This study was desinged to investigate the role of frequency of atrial contraction compared to acute increases in right atrial pressure in the regulation of atrial natriuretic peptide (ANP) release in humans. The studies were performed in patients undergoing electrophysiological study. In group I (n = 12) the rate of atrial contraction was increased by continuous rapid right atrial pacing at a rate of 120 beats/min (bpm; group IA; n = 6) or 176 bpm (group Ib; n = 6) for 5 min. No increases in atrial pressure or circulating ANP occurred in response to atrial tachycardia. In contrast, continuous rapid right ventricular pacing (group II; n = 12) at ventricular rates of 120 bpm (group IIa; n = 6) and 150 bpm (group IIb; n = 6) increased both right atrial pressure and ciruculating ANP. These results demonstrate that, in contrast to studies in vitro, increases in the frequency of atrial contraction in the absence of increases in atrial pressure do not release atrial natriuretic peptide. These studies, therefore, support the conclusion that atrial pressure is the primary physiological stimulus for ANP.