Role Of Autonomic Nervous System In The Regulation Of Atrial Natriuretic Peptide Release

Objective: Atrial natriuretic peptide (ANP) is a potent diuretic and natriuretic hormone. It is important for the regulation of blood pressure and body fluid. The purpose of the present study was to define the role of autonomic nervous system(ANS) in the regulation of ANP release in the atia from euthyiod and hyperthyroid rabbits. This study provides a rationale for the clinical treatment of cardiac disease.Methods: New Zealand White rabbit of either sex weighing 2 kg were used. Rabbits were subcutaneously injected with L-thyroxine (0.5 mg/kg daily) or vehicle for 2 weeks.①Isolated perfused beating atrial model:Experiment were performed in the isolated perfused beating atria and vagus nerve-right atria. Measuring of cardiac index and HE staining of cardiac myocytes were performed in the evaluation of cardiac hypertrophy from hyperthyroid rabbits. The atria were perfused for 60 min to stabilize ANP secretion. [3H]Inulin was introduced to the pericardial fluid 20 min before the start of the sample collection. The perfusate was collected at 2-min intervals at 4°C for analyses. The control period (48 min) was followed by an infusion of acetylcholine(ACh) in order to observe the effect of ACh alone. The control period (12 min) was followed by an infusion of isproterenol(ISO) for 36 min, and ISO was followed by an infusion of ACh for 36 min.②Isolated vagus nerve–right atrial model : Separate vagus nerve from the carotid artery .Open the thorax and cut the aorta. Transfer the preparation of vagus nerve–right atrium model into buffer-filled organ chamber. Pericardium sample was collected at 2-min intervals at 4°C for analyses. The immunoreactive ANP in perfusate and pericardium was measured by radioimmunoassay(RIA).Results:①Exogenous ACh increased atrial myocyte ANP release concomitantly with a decrease in atrial stroke volume and pulse pressure in the physiological conditions.②ISO decreased atrial ANP release concomitantly with a increase in atrial stroke volume and pulse pressure in the physiological conditions.③ISO accentuated the ACh -induced increase in atrial ANP release in the physiological conditions.④T he effect of ACh -induced increase in atrial ANP release was attenuated in the pathophysiology of hyperthyroid heart.⑤The effect of ISO accentuated the ACh -induced increase in atrial ANP release was attenuated in the pathophysiology of hyperthyroid heart.⑥Endogenous ACh increased atrial ANP release concomitantly with a decrease in heart rate and atrial tension in the pathophysiological conditions.Conclusions: These findings indicate that ANS has an important role in the regulation of ANP release under the physiological conditions. The present study also shows that alterd role of ANS in the regulation of atrial ANP release is involed in the pathophysiology of hyperthyroid heart.