Increased concentration of plasma cyclic GMP during aconitine-induced atrial fibrillation in dogs and paroxysmal atrial fibrillation in patients.

The concentrations of cyclic nucleotides were measured by radioimmunoassay in the plasma of dogs with aconitine-induced atrial fibrillation and of patients with paroxysmal atrial fibrillation. The concentration of cyclic GMP in the plasma of dogs was significantly elevated 30 and 60 min after the onset of atrial fibrillation, whereas the concentration of cyclic AMP showed no significant changes. In dogs without atrial fibrillation there was no significant change in the plasma concentrations of either cyclic GMP or cyclic AMP. Intravenous injection of 0.1 mg/kg atropine into dogs with atrial fibrillation and with increased plasma cyclic GMP converted 7 of 10 animals to normal sinus rhythmus, whereupon the plasma levels decreased to normal. We found a significant increase of cyclic GMP in the left ventricle 30 min after onset of atrial fibrillation as well as significant increase of cyclic AMP in the left atrium 60 min after onset. The concentration of cyclic GMP in the plasma of patients with attacks of paroxysmal atrial fibrillation was significantly higher than in those with sinus rhythmus. No significant changes of plasma cyclic AMP levels were observed in these patients during atrial fibrillation.