Cortisol regulates Na+ uptake in zebrafish, Danio rerio, larvae via the glucocorticoid receptor

► Cortisol stimulates Na+ uptake and ammonia excretion in zebrafish larvae through glucocorticoid receptor. ► The stimulation of Na+ uptake in larvae during acid-exposure is at least partially mediated by increased cortisol level. ► Cortisol stimulates Na+ uptake by stimulating the recently proposed NHE3b-Rhcg1 functional metabolon. ► Glucocorticoid receptor is highly expressed in ionocytes responsible for Na+ uptake.