Norepinephrine-induced atriopeptin release in conscious dogs is mediated by alterations in atrial pressure

This study was designed to determine whether the increase in atriopeptin secretion induced by an intravenous infusion of norepinephrine is mediated directly by adrenergic receptor stimulation or indirectly by the associated increase in atrial pressure. Norepinephrine was infused at 0.5 μg·kg t-1 ·min −1 for 30 min into both sham-operated (intact) and cardiac-denervated conscious dogs. The infusion increased mean arterial pressure all dogs. On the other hand, left atrial pressure increased from 5.0±0.7 to 9.6±1.6 mmHg (p < 0.01) in intact dogs, but decreased from 5.5±1.0 to 2.0±0.7(p < 0.01) in cardiac-denervated dogs. Right atrial pressure changes followed similar trends, but were not significant in the intact group. Plasma atriopeptin increased from 73±12 to 110±18 pg/ml (p < 0.01) as left atrial pressure increased in intact dogs and decreased from 79±15 to 54±10 pg/ml(p < 0.01) as left atrial pressure decreased in cardiac-denervated dogs. The changes in plasma atriopeptin correlated closely with the changes in left atrial pressure (r = 0.941, p < 0.001) and to a lesser extentent with the changes in right atrial pressure (r = 0.413, p < 0.05). These results suggest that the change in plasma atriopeptin induced by infusion of norepinephrine into conscious dogs in mediated by the ocncomitant change in atrial pressures.