We examined the renoprotective effects of l-carnosine (-alanyl-l-histidine) on ischemia/reperfusion (I/R)-induced acute renal failure (ARF) in rats. Ischemic ARF was induced by occlusion of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. In vehicle (0.9% saline)-treated rats, renal sympathetic nerve activity (RSNA) was significantly augmented during the renal ischemia, and renal function was markedly decreased at 24 h after reperfusion. Intracerebroventricular injection of l-carnosine (1.5 and 5 pmol/rat) to ischemic ARF rats dose-dependently suppressed the augmented RSNA during ischemia and the renal injury at 24 h after reperfusion. N-␣-Acetyl-l-carnosine [N-acetyl--alanyl-l-histidine; 5 pmol/rat intracerebroventricular (i.c.v.)], which is resistant to enzymatic hydrolysis by carnosinase, did not affect the renal injury, and l-histidine (5 pmol/rat i.c.v.), a metabolite cleaved from l-carnosine by carnosinase, ameliorated the I/R-induced renal injury. Furthermore, a selective histamine H 3 receptor antagonist, thioperamide (30 nmol/rat i.c.v.) eliminated the preventing effects by l-carnosine (15 nmol/rat intravenously) on ischemic ARF. In contrast, a selective H 3 receptor agonist, R-␣-methylhistamine (5 pmol/rat i.c.v.), prevented the I/R-induced renal injury as well as l-carnosine (5 pmol/rat) did. These results indicate that l-carnosine prevents the development of I/R-induced renal injury, and the effect is accompanied by suppressing the enhanced RSNA during ischemia. In addition, the present findings suggest that the renoprotective effect of l-carnosine on ischemic ARF is induced by its conversion to l-histidine and l-histamine and is mediated through the activation of histamine H 3 receptors in the central nervous system.
We investigated whether the treatment with 17 beta-oestradiol has renal protective effects in male rats with ischaemic acute renal failure (ARF). We also examined if the effect of 17 beta-oestradiol is accompanied by suppression of enhanced endothelin-1 production in postischaemic kidneys. Ischaemic ARF was induced by clamping the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. Renal function parameters such as blood urea nitrogen, plasma creatinine and creatinine clearance were measured to test the effectiveness of the steroid hormone. Renal function in ARF rats markedly decreased 24 h after reperfusion. The ischaemia/reperfusion-induced renal dysfunction was dose-dependently improved by pretreatment with 17 beta-oestradiol (20 or 100 microg/kg, intravenously). Histopathological examination of the kidney of untreated ARF rats revealed severe lesions, such as tubular necrosis, proteinaceous casts in tubuli and medullary congestion, all of which were markedly improved by the higher dose of 17 beta-oestradiol. In addition, endothelin-1 content in the kidney after the ischaemia/reperfusion increased significantly by approx. 2-fold over sham-operated rats, and this elevation was dose-dependently suppressed by the 17 beta-oestradiol treatment. These results suggest that oestrogen exhibits protective effects against renal dysfunction and tissue injury induced by ischaemia/reperfusion, possibly through the suppression of endothelin-1 overproduction in postischaemic kidneys.
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