Cortisol is an osmoregulatory and glucose-regulating hormone in Atlantic sturgeon, a basal ray-finned fish.

Our current understanding of the hormonal control of ion regulation in aquatic vertebrates comes primarily from studies on teleost fishes, with relatively little information on more basal fishes. We investigated the role of cortisol in regulating seawater tolerance and its underlying mechanisms in an anadromous chondrostean, the Atlantic sturgeon (). Exposure of freshwater-reared Atlantic sturgeon to seawater (25 ppt) resulted in transient (1-3 day) increases in plasma chloride, cortisol and glucose levels and long-term (6-14 day) increases in the abundance of gill Na/K/2Cl cotransporter (NKCC), which plays a critical role in salt secretion in teleosts.