[Endothelin action on the arterial pressure and venous tonus in waking rats with normal and artificially enhanced levels of atriopeptide in the blood].

The effects of endothelin (0.1 and 1 nmol/kg into the left ventricle) on mean blood pressure (MAP), heart rate (HR), central venous pressure (CVP), and mean circulatory filling pressure (MCFP) were investigated in conscious and unrestrained WKY rats before and during continuous infusion of atriopeptide (1 mu mk/kg/min i.v.). In intact rats, bolus injection of endothelin into the left ventricle caused a transient hypotension followed by a long-term increase in MAP. In the rats receiving atriopeptide infusion constantly, the hypotensive phase of endothelin effects was augmented whereas the hypertensive phase was reduced. Low doses of endothelin did not affect CVP and MCFP while the highest dose given to intact rats and atriopeptide-treated rats caused small, but significant decreases in CVP and MCFP. Our results suggest that endothelin has small effects on total body's venous tone in contrast to its effectiveness by increasing blood pressure.