Renoprotective effect of yohimbine on ischaemia/reperfusion-induced acute kidney injury through α2C-adrenoceptors in rats

Excitation of renal sympathetic nervous activity and the resulting increased levels of renal venous norepinephrine play important roles in renal ischaemia/reperfusion injury in rats. This study examined the effects of yohimbine, a non-selective α2-adrenoceptor antagonist, on renal venous norepinephrine levels and kidney function in acute kidney injury. Acute ischaemia/reperfusion-induced kidney injury was induced in rats by clamping the left renal artery and vein for 45 min, followed by reperfusion, 2 weeks after a contralateral nephrectomy. Intravenous injection of yohimbine (0.1 mg/kg) 5 min prior to ischaemia significantly attenuated kidney injury and decreased the renal venous norepinephrine levels, as compared with vehicle-treated rats. To investigate the involvement of α2-adrenoceptor subtypes, we pre-treated with JP-1302, a selective α2C-adrenoceptor antagonist (1 mg/kg). This suppressed renal venous norepinephrine levels and tumour necrosis factor-α and monocyte chemoattractant protein-1 mRNA levels after reperfusion and improved kidney function. Pre-treatment with BRL44408, a selective α2A-adrenoceptor antagonist (1 mg/kg), or imiloxan, a selective α2B-adrenoceptor antagonist (1 mg/kg) had no effect on renal function or tissue injury. These results suggest that yohimbine prevented ischaemia/reperfusion-induced kidney injury by inhibiting α2C-adrenoceptors and suppressing pro-inflammatory cytokine expression.