Effect of ouabain on hemodynamics in acute volume expanded hypertensive dogs

To evaluate possible roles of endogenous Na+-K+-ATPase inhibitors in vasoconstricted blood pressure elevation produced by acute volume expansion, we administered ouabain (Na+-K+-ATPase inhibitor) intravenously (30 micrograms/kg) for 10 min to dogs, 3 h after volume expansion with dextran in lactated Ringer's solution (20 ml/kg, for 1 h). Acute volume expansion resulted in the elevation of blood pressure associated with an increase in cardiac output. In some dogs the blood pressure remained elevated with gradual increase in total peripheral resistance (Group I) or with sustained high cardiac output (Group II), and in other dogs (Group III) it returned to the control level. Ouabain administration elevated the blood pressure and total peripheral resistance in these groups and sham dogs which did not have volume expansion. And these effects of ouabain were not correlated with the degree of blood pressure or vasoconstriction produced by volume expansion. Thus, it is not likely that endogenous Na+-K+-ATPase inhibitors increased to produce vasoconstricted hypertension after acute volume expansion.