To explore an interaction(s) of endothelin with other blood pressure regulating systems, effects of either a high concentration of sodium chloride vehicle or pretreatment with atrial natriuretic peptide (ANP) on the pressor response to endothelin were investigated in rats.

Sprague-Dawley rats were anesthetized with thiopental (50mg/kg, IP) and were cannulated into left lateral cerebral ventricle. The left femoral artery and vein were also catheterized to measure blood pressure and to serve as an infusion route, respectively. Endothelin (10pmol) dissolved in either normal (0.15M) or high concentration (3.0M) of NaCl vehicle with ANP (1 nmol, ICV). For intravenous (IV) infusion, endothelin(1pmol/min) dissolved either in normal or high concentration of NaCl vehicle was infused for 20min.

ICV endothelin caused an increase of arterial pressure, in which the NaCl did not affect but ANP-pretreatment significantly attenuated the pressor magnitude. IV endothelin also increased the arterial pressure, which was potentiated by NaCl, ie, the maximum increase caused by the IV endothelin in the high NaCl vehicle was greater than the sum of that induced by endothelin (infused in normal NaCl vehicle) and that induced by high NaCl vehicle only.

These results suggest that endothelin has separate central and peripheral pressor actions, in which the former is not affected by high NaCl but is attenuated by the ANP system and the latter is potentiated by high NaCl.