Figure 4.

HS regulates PCSK6–corin–ANP–AQP2/β-ENaC pathway in the rat kidney and M1-CCD cells. (a–d) Rats were fed with HS diet together with or without K⁺ for 1, 3, and 7 days (n = 8 for each group) or a normal diet for 3 days (control group, n = 8). ELISA and Western blot and were used to measure serum and renal levels of corin and ANP in diet groups. (e) Immunohistochemistry of protein level of corin in the renal cortex and medulla. Scale bar: 50 µm. (f–m) Real-time qPCR quantification of renal PCSK6, ANP, AQP2, and β-ENaC mRNA levels in diet groups (f–i) and mRNA level of corin, PCSK6, AQP2, and β-ENaC in M1-CCD cells transfected with corin, PCSK6, or control siRNA for 24 hour, then treated with 20 mM NaCl for 24 hour (j–m). Data are mean ± SEM *P < 0.05. Abbreviations: ANP, atrial natriuretic peptide; AQP2, aquaporin 2; β-ENaC, β-epithelial Na⁺ channel; HS, high-salt; LS, low-salt; M1-CCD, M1-cortical collecting duct; PCSK6, proprotein convertase subtilisin/kexin-6.