Effectiveness of the aldosterone-sodium and -potassium feedback control system

Abstract

This study was conducted to determine the quantitative importance of the aldosterone feedback mechanism in controlling each one of three major factors that have often been associated with aldosterone, namely, extracellular fluid sodium concentration, extracellular fluid potassium concentration, and extracellular fluid volume. To do this, the ability of the body to control these three factors in the face of marked changes in daily sodium or potassium intake was studied under two conditions: 1) in the normal dog, and 2) in the dog in which the aldosterone feedback mechanism was prevented from functioning by removing the adrenal glands and then providing a continuous fixed level of supportive aldosterone and glucocorticoids during the low and high electrolyte intake periods. Under these conditions, removal of feedback control of aldosterone secretion decreased the effectiveness of plasma potassium control by nearly fivefold (39% vs. 8% change in plasma potassium concentration), fluid volume by sixfold (12% vs. 2% change in sodium space) and had no effect on control of plasma sodium concentration (2% change with and without feedback control of aldosterone secretion.)

Effects of adrenalectomy and chronic adrenal corticosteroid replacement on potassium transport in rat kidney.

“…Chronic adrenal insufficiency is associated with hyperkalemia and with a decreased ability to excrete an acute potassium load (5-1 1). Young et al (12)(13)(14) have demonstrated the importance of chronic aldosterone replacement in adrenalectomized dogs in maintaining potassium homeostasis. Thus, restoration of plasma aldosterone in glucocorticoid replete, aldosterone-deficient animals lowers plasma potassium to basal levels and normalizes the relationship between plasma potassium concentration and urinary excretion of potassium.…”

Lack of Prolonged Effect of Antidiuretic Hormone on the Renin‐aldosterone System in the Dog

“…On the second control day "Na space (determined by the 3-h dilution of a known amount of "Na given intravenously) Young et al, 1976), and body weight were measured.…”

“…The experiments were carried out in six healthy mongrel dogs whose weight averaged 22 kg. Chronically implanted arterial and venous catheters were placed as described previously (Cowley, Liard & Guyton, 1973Young et al, 1976). Following surgical recovery the dogs were housed in metabolic cages and fed a controlled diet containing 10 mmol/day of sodium and 30 mmol/day potassium.…”

“…After 5 days of adjustment to the cages and diet, the following measurements were made on two consecutive days: plasma and urine sodium and potassium concentration (by flame photometry), a 24-h urine volume and water intake (drinking and food), urine osmolarity (by freezing-point depression), plasma renin activity by method of Haber et al (1969), plasma aldosterone concentration by radioimmunoassay (McCaa et al, 1972), and plasma cortisol concentration as described by Murphy (1967). On the second control day "Na space (determined by the 3-h dilution of a known amount of "Na given intravenously) Young et al, 1976), and body weight were measured.…”

Systemic effects of ingesting varying amounts of a commercial carbohydrate beverage postexercise.

“…Aldosterone is increased after exercise [31]. Among the factors known to regulate aldosterone secretion, K is considered one of the most potent [32]. The observed decline in serum K. may therefore have mediated the more rapid decline of aldosterone observed in the CHO condition.…”