To examine whether release of atrial natriuretic factor (ANF) can explain the increase in sodium excretion during supraventricular tachycardia, we compared the natriuretic responses with right atrial pacing tachycardia and ANF infusion in six barbiturate-anesthetized dogs. When we raised the dogs' heart rates from 148 +/- 12 to 263 +/- 12 beats/min for 30 min, plasma immunoreactive (IR) ANF rose from 42.1 +/- 3.4 to 139.0 +/- 25.6 pg/ml. Sodium excretion increased from 36.2 +/- 12.8 to 132.4 +/- 40.8 mumol/min in the exposed denervated kidney. When we infused 12.5 ng.min-1.kg body wt-1 of ANF at a spontaneous heart rate of 146 +/- 12 beats/min, plasma IR-ANF rose from 46.0 +/- 5.1 to 121.7 +/- 17.5 pg/ml, which was similar to that observed during pacing tachycardia. Sodium excretion increased from 40.6 +/- 11.3 to 193.6 +/- 46.0 mumol/min, which was higher than that observed during pacing tachycardia. Renal blood flow was lower during pacing tachycardia than during ANF infusion, but glomerular filtration rate and aortic blood pressure were not significantly different during the two procedures. Because sodium excretion was 30% lower during pacing tachycardia, even though plasma IR-ANF was as high as during ANF infusion, we conclude that ANF induces the acute rise in sodium excretion during pacing tachycardia but that hemodynamic changes may attenuate the natriuretic response.