Corticosteroid control of Na+/K+-ATPase in the intestine of the sea lamprey (Petromyzon marinus)

•Lamprey steroids 11-deoxycortisol (S) and deoxycorticosterone (DOC) were examined.•Corticosteroid receptors in the intestine had higher binding affinity for S than DOC.•Na+/K+-ATPase (NKA) is a target of corticosteroid control in the lamprey intestine.•Treatment with S, but not DOC, increased intestinal NKA expression and activity.•Treatment with S improves the capacity for osmoregulation in seawater.•Control of intestinal osmoregulation by corticosteroids is a basal vertebrate trait.