Figure 6. Effect of hyposmotic shock on Na⁺/K⁺-ATPase (NKA) activity in the kidney, and on mRNA expression of SaDRD1 in vitro, with and without exogenous dopamine treatment.

(A) NKA activity in kidneys isolated from fish over a 7 day period following transfer to FW. (B) Effects of dopamine (1 μM and 10 μM) on the relative expression of SaDRD1 mRNA in renal primary cells cultured in isosmotic medium. All the data was normalized to control cells (without dopamine, = 1). (C) Changes of SaDRD1 mRNA expressions for renal primary cells after exposure to the hypoosmotic medium (100 mOsmol/L). (D) Effects of hypoosmotic stress and exogenous dopamine on NKA activity in cultured renal primary cells. The hypoosmotic shock and dopamine treatment occurred concurrently. β-actin was used as an internal control. The results are presented as the mean ± S.E.M. of the data from 3 replicates (In vivo: every biological repeat comprising 5 individuals pooled together; In vitro: 3 wells in one experiment). *p < 0.05; **p < 0.01; ***p < 0.001.