The relationship of plasma aldosterone-binding globulin to blood pressure regulation in young adults with cystic fibrosis.

Findings of increased secretion rate and decreased metabolic clearance rate (MCR) of aldosterone in patients with cystic fibrosis of the pancreas (CF) and our own evidence on the association of increased aldosterone-binding globulin (ABG)-binding and decreased MCR in essential hypertension (EH) inspired us to investigate the plasma aldosterone, with the inclusion of protein-binding variables, in CF patients. (1) The percentage of plasma aldosterone specifically bound to ABG was measured in 55 young adults with CF in addition to total plasma aldosterone, total plasma corticosteroids and for comparison of corticosteroid-binding globulin (CBG)-binding capacity. (2) The percentage of ABG-bound plasma aldosterone was found to vary with the seasonal change in temperature and the hepatic function of CF patients. Many of the CF patients, particularly during spring, summer and fall, had elevated plasma ABG-bound aldosterone which would be expected to result in low MCR. This binding was less elevated during cooler weather, suggesting that ABG-bound aldosterone is participating in the adaptation to warmer weather by probably increasing extrarenal sodium retention, thereby preventing a fall of blood pressure (BP) to pathologically low levels. A significant correlation was consequently found between the ABG capacity and the ambient temperature. (3) CF patients with low liver function had significantly lower protein binding of aldosterone and only slightly lower CGB capacity, presumably due to disturbed protein synthesis by the liver. (4) In some patients, elevated total plasma aldosterone and total corticosteroids were found, probably as a result of an adaptation to excessive sweat losses of sodium and the consequent contraction of intravascular volume. (5) Our findings also demonstrated a positive correlation between plasma ABG-bound aldosterone and both systolic and diastolic BP.