Life Sciences, hypoosmotic regulation, Na + /K + ATPase, Zoology, gill epithelium, chloride cells, Russian sturgeon Acipenser gueldenstaedtii, somatotropin, Transformation, Osmolarity, Epithelial cells, Growth, Body weight, Chloride transport, Osmoregulation, Hormones, Juveniles, Na+/K+-exchanging ATPase, Cells, Salinity, Enzymatic activity, Ultrastructure,...