Atrial natriuretic peptide in humans. Production and clearance by various tissues.

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Abstract
Although it is assumed that the human heart secretes atrial peptides, direct proof is not available. We therefore measured immunoreactive atrial natriuretic peptide levels in coronary sinus blood and simultaneously in femoral arterial and venous blood from patients before and during stepwise incremental atrial pacing of up to 200 beats per minute. Since the fate of circulating atrial peptides is unknown, we also measured immunoreactive atrial natriuretic peptide concentrations in arterial and venous blood across the liver, kidney, lower limb, and lung in patients undergoing cardiological investigation. Peptide levels in coronary sinus blood were higher than in samples from the femoral artery or vein. As the heart rate was accelerated by atrial pacing, peptide concentrations increased in coronary sinus blood and to a lesser extent in peripheral samples. Whereas the levels in venous blood draining the liver, kidney, and lower limb were approximately 50% of those in arterial blood, concentrations were similar in samples drawn simultaneously from the pulmonary artery and the aorta. These results show that the human heart produces immunoreactive atrial natriuretic peptide and that secretion increases with atrial tachycardia. The liver, kidney, and lower limb remove the peptide from arterial blood, but there is little change in its concentration during circulation of blood through the lungs.