Diuresis and Natriuresis during Volume Expansion following Cardiac Reinnervation ∗

Abstract

In a previous study it was reported that in the chronic cardiac denervated dog the natriuretic and diuretic responses to acute isotonic, iso-oncotic intravascular volume expansion are significantly attenuated (1). Subsequently it was reported by Knox and associates (2) that the natriuretic response to an acute isotonic sodium chloride load is also attenuated in the same preparation. These studies suggest that cardiac nerves influence both sodium and water excretion. The present report describes experiments which were carried out on three dogs at least 3 years after surgical denervation of the heart to determine if reinnervation is associated with a return of the normal diuretic and natriuretic response to intravascular expansion.

Methods. The methods employed in these experiments are essentially those reported previously (1). All experiments were carried out under pentobarbital sodium anesthesia (30 mg/kg). A small branch of the femoral artery was cannulated for blood pressure recording and for obtaining blood samples. Drugs were administered through a catheter introduced through a needle into a foreleg vein. Urine samples were obtained through a catheter inserted into the bladder. Following these preparations urine was collected in graduated cylinders until at least 2 ml of urine were obtained. The bladder was then flushed with water and air. A blood sample was obtained between two such collection periods that showed similar urine flows. Dextran (6% clinical dextran and isotonic saline) was then infused in an amount equal to 3% body weight at a rate of approximately 30 ml/min. When urine flow achieved a new steady level, blood and urine samples were again obtained and the experiment continued until urine volume declined. At the end of the experiment the bladder was flushed with Furacin solution, antibiotics were administered, catheters were removed and the animals were returned to the kennels for recovery.