Age-related change and its significance of BKCa in renal artery smooth muscle cells of spontaneously hypertensive rats

Objective To observe the change of large-conductance calcium-activated potassium channels(BKCa,MaxiK) along with age and its relationships with blood pressure, renal vascular remodeling and glomerular filtration rate(GFR) in rats. Methods Eighteen male spontaneously hypertensive rats(SHR) aged 15, 21, 27 weeks as hypertension group, and eighteen corresponding aged normal rats as control group were selected. Abdominal aortic blood pressure of rats were measured. The urine creatinine and serum creatinine value in 24 hours were tested, and calculated creatinine clearance rate(Ccr), which was on behalf of GFR. The potassium current, capacitance of membrane(Cm) of vascular smooth muscle cells(VSMCs) of renal artery were recorded, and the BKCa current, the potassium current density and the BKCa current density were calculated. The renal arteries were stained to observe the changes of blood vessel morphous along with age, including vessel lumen diameter(LD), media thickness(MT) and MT/LD. Results The mean abdominal aortic blood pressure(MABP) of SHR in different aged groups was obviously higher than that of normal rats(P0.05). The Cm of renal arterial VSMCs increased with age in SHR group, but it wasn't in normal group. The BKCa current density of SHR renal arterial VSMCs decreased with age, but the change of normal rats with age had no significant difference. The LD of SHR renal arteries decreased with age and MT, MT/LD of renal arteries in SHR increased with age(P0.05), but it wasn't found in normal group. Compared with normal group, the GFR of SHR group significantly decreased. The BKCa current density was correlated with Cm, MABP, LD, MT, MT/LD and GFR in SHR(r was -0.7962, -0.7361, 0.8275, -0.7923, -0.6492, -0.7612 respectively), but it was correlated with MABP only in normal group(r=-0.4761). Conclusion BKCa current and current density have a age-related decline in SHR, and the decline was highly correlated with the vascular remodeling of hypertension and GFR.