Stimulation of Aldosterone Secretion by Hemorrhage in Dogs after Nephrectomy and Decapitation

In eight intact, anesthetized dogs the aldosterone secretory rate averaged 13.8 ± 1.9 ng/min (mean ± SE). One hour after nephrectomy and decapitation, the aldosterone secretory rate decreased to 2.3 ± 1.7 ng/min and failed to increase in response to hemorrhage. By 8 hours after surgery, the aldosterone secretory rate had returned to control levels. The serum potassium concentration gradually increased from 3.2 ± 0.5 mEq/liter in the control samples to 5.3 ± 0.5 mEq/liter in the 8-hour samples. Eight hours after nephrectomy and decapitation, the arterial blood pressure was lowered to 70 mm Hg by hemorrhage in six dogs. During the next 3 hours, the aldosterone secretory rate increased from 11.2 ± 2.1 ng/min to 27.3 ± 2.1 ng/min. Associated with the increase in the aldosterone secretory rate following hemorrhage was a further increase in the serum potassium concentration from 5.3 ± 0.5 mEq/liter to 6.8 ± 0.5 mEq/liter. The aldosterone secretory rate did not increase following hemorrhage when the rise in serum potassium concentration was prevented by hemodialysis. These data indicate that normal levels of aldosterone secretion can be maintained in the absence of the renin-angiotensin system and the pituitary secretion of adrenocorticotropic hormone. Also, hemorrhage will greatly enhance aldosterone secretion in the absence of the head and the kidneys but only if the serum potassium concentration is allowed to rise following the hemorrhage.