Abstract: Objective: To investigate the relationship between the level of oxidative stress and the expression of intermediate conductance calcium activated potassium channel (K_Ca3.1) protein in the cardiac fibroblasts (CFs) during hypertension process,and to clarify the role of K_Ca3.1 in cardiac fibrosis and its mechanism. Methods: The CFs of male C57B6 and AGT-REN double transgenic hypertension (dTH) mice were cultured and the wild C57B6 mouse CFs were used as control group. The CFs of dTH mice were randomly divided into high blood pressure group (dTH) and N-acetyl cysteine group (NAC). The CFs were treated with different concentrations of NAC for 24 h. The cell proliferation was detected by MTT and double dichlorofluorescein (DCFH-DA) probe was used for the detection of cellular reactive oxygen species (ROS) expression; Western blotting was employed to detect the expressions of collagen Ⅰ, collagen Ⅲ, K_Ca3.1 channel protein and the changes of PI3K signaling pathway protein phosphorylation. Results: The ROS production and protein expression of K_Ca3.1 channel of the dTH mice on 4, 8, 12 months were increased compared with 2 months(P<0.05 or P<0.01); the results of MTT suggested that the proliferation rates of CFs were 165.9%,138.72%,110.92% and 109.82% after administration of 1×10^-6,1×10^-5,1×10^-4 and 1×10^-3 mol·L^-1 NAC in the dTH mice, and 1×10^-4 and 1×10^-3 mol·L^-1 NAC significantly inhibited the proliferation of CFs.Compared with control group,the secretion of collagen Ⅰ and Ⅲ of CFs in the TH mice was decreased in 1×10^-4 mol·L^-1 NAC group(P<0.01).The results of Western blotting showed that compared with control group, the expression level of K_Ca3.1 channel protein in CFs of the TH mice in 1×10^-4 mol·L^-1 NAC group was decreased(P<0.01). Compared with control group,the p-AKT/T-AKt in CFs of the dTH mice was increased (P<0.01); but in NAC group,the p-AKT/T-AKt was lower than that in dTH group (P<0.01). Conclusion: NAC can inhibit the expression of K_Ca3.1 channel protein in CFs of the dTH hypertensive mice, which may be related to increasing the phosphorylation of AKt/PI3K signaling pathway.

Key words: myocardial fibrosis, cardiac fibroblasts, intermediatec onductance Ca²⁺-activated K⁺ channels, reactive oxygen species