Aldosterone response to renin, angiotensin, ACTH, hemorrhage and sodium depletion in a freshwater teleost, Catostomus macrocheilus

Abstract

1. 1. Plasma aldosterone activity (PAA) was measured in individual large-scale suckers ( Catostomus macrocheilus) by radioimmunoassay. 2. 2. PAA in control groups was 12.0 ± 6.0 (mean ± SEM) pg/ml; one control group showed a sixfold elevation of PAA, possibly reflecting a seasonal effect. 3. 3. Injections of sucker renin preparation, synthetic angiotensin II and synthetic adrenocorticotrophin had no effect upon PAA. PAA was also unaffected by sodium depletion, sodium loading and moderate hemorrhage. 4. 4. Prolonged restraint stress coupled with severe hemorrhage significantly increased PAA to 47.1 ± 5.1 pg/ml. 5. 5. This study indicates that aldosterone secretion in teleost fish has either rudimentary or yet to be discovered controls and functions.