Molecular and physiological responses to long-term sublethal ammonia exposure in Atlantic salmon (Salmo salar)

► Rhcg1 plays an important role in ammonia excretion in Atlantic salmon parr during long-term exposure to sublethal ammonia contrary to the results of acute exposure studies. ► The first evidence of an up-regulation of branchial transcription of the genes encoding the Rhesus (Rh) glycoproteins, Rhcg1 and Rhcg2, urea transporter (UT) and aquaporin 3a (Aqp3a), during long-term ammonia exposure in fish. ► Gln synthesis is an ammonia detoxifying strategy employed in the brain of Atlantic salmon parr during long-term sublethal ammonia exposure.