Mechanism of action of nitroglycerin during exercise in a rat model of heart failure. Improvement of blood flow to the renal, splanchnic, and cutaneous beds.

The radioactive microsphere technique was used to trace regional blood flow and total cardiac output distribution in rats in heart failure secondary to biventricular volume overload during acute intravenous infusion of nitroglycerin. Data from rats with heart failure (chronic arteriovenous shunt) were compared to data obtained from rats subjected to sham surgical procedures. In both glycerin and normal saline (control). In heart failure, nitroglycerin slightly increased cardiac output at rest and during exercise, increased stroke volume, and reduced systemic vascular resistance at rest but not during exercise. In the heart failure group, exercise reduced flow to the renal, gastrointestinal, and cutaneous circulations but had little or no effect in the sham group. Nitroglycerin dramatically increased renal, gastrointestinal, and cutaneous blood flow during exercise in the heart failure group but had minimal effects on active hyperemia in the skeletal muscle bed. In the sham group, nitroglycerin decreased blood flow in the renal, gastrointestinal, and cutaneous beds and had no effect on skeletal muscle blood flow. Thus, in the renal, gastrointestinal, and cutaneous circulations during exercise, nitroglycerin increased flow in the heart failure group and decreased flow in the sham group to the extent that the respective values in the two groups were equal.