INCREASED PLASMA ATRIAL-NATRIURETIC-PEPTIDE AFTER ACUTE INJECTION OF ALCOHOL IN RATS

A number of mechanisms may be involved in the protective effect of low ethanol (ETOH) consumption on the development of the age-dependent hy pertension in both human and experimental animals. It was the objectiv e of the present study to test the hypothesis that acute administratio n of low doses of ETCH would increase the plasma content of atrial nat riuretic peptide (ANP), a hormone known to decrease blood pressure. Pl asma ANP levels were increased significantly within 15 min after the i .p. injection of 1 or 2 g of ETOH/kg b.wt. The increase in plasma ANP was more pronounced and longer lasting after the i.p. injection of 2 r ather than 1 g of ETOH/kg b.wt. This increase in plasma ANP level was associated with a rapid decrease of atrial ANP, but not of ventricular ANP which on the contrary was significantly elevated at 120 min posti njection. It has been suggested that opioids could play a significant role in controlling ANP release. In fact, circulating levels of beta-e ndorphin were also rapidly increased after the ETOH injection, with a timecourse pattern similar to that of ANP. Furthermore, a highly posit ive correlation was found between the ETOH-induced changes of plasma A NP and p-endorphin contents. Significant increases in plasma corticost erone and adrenocorticotropic hormone, but not aldosterone contents, w ere observed after the i.p. injection of 2 g of ETOH/kg b.wt., whereas plasma arginine vasopressin levels were significantly decreased at 15 but not at 120 min postethanol. There was no significant elevation in blood pressure during the 120-min experimental period, although a sma ll tachycardia did develop in the FTOH-treated animals. Thus, acute in vivo administration of ETCH increased plasma ANP content in a dose-de pendent manner and may play a role in the ''protective'' effect of low ETOH consumption in the development of the age-dependent hypertension .