[Effect of dexamethasone and ACTH on plasma atrial natriuretic polypeptide levels during hemorrhage in rats]

Anti-shock effect of dexamethasone (Dexa) and ACTH on atrial natriuretic polypeptide (ir-ANP) secretion was studied during hemorrhage in rats as reflected in the plasma ir-ANP, corticosterone (Comp B) and ACTH levels. We also observed the number of survived rats and plasma ir-ANP levels stimulated by volume loading of the shed blood or fluid. The rats were divided into non-treated group (saline), Dexa group (Dexa 5mg.kg-1) and ACTH group (ACTH 200 micrograms.kg-1). They were anesthetized by intravenous injection of pentobarbital sodium 30 mg.kg-1. Atrial blood sample for control value was collected before hemorrhage. Approximately 20% and then 30% of the estimated blood volume was taken for hemorrhage. Hemorrhage induced significant reductions in plasma ir-ANP levels. They decreased from a control value of 133.8 +/- 6.1 pg.ml-1 to 76.6 +/- 4.2 pg.ml-1 (P less than 0.005), but plasma levels of Comp B and ACTH increased markedly. The ir-ANP secretion increased in response to the elevation of atrial pressures after volume loading. The administration of Dexa and ACTH to the rats tended to inhibit the reduction of plasma ir-ANP levels during hemorrhage and improved the survival rate 24hr after bleeding 30% of the estimated blood volume.