Low concentrations of carbon monoxide (CO) can protect tissues against ischemia-reperfusion (I-R) injury. We have recently identified a novel class of compounds, CO-releasing molecules (CO-RMs), which exert important pharmacological activities by carrying and delivering CO to biological systems. Here, we examined the possible beneficial effects of CO liberated from CO-RMs on the damage inflicted by cold storage and I-R in isolated perfused kidneys. Hemodynamic and biochemical parameters as well as mitochondrial respiration were measured in isolated perfused rabbit kidneys that were previously flushed with CO-RMs and stored at 4 degrees C for 24 h. Two water-soluble CO-RMs were tested: (1) sodium boranocarbonate (CORM-A1), a boron-containing carbonate that releases CO at a slow rate, and (2) tricarbonylchloro(glycinato)ruthenium(II) (CORM-3), a transition metal carbonyl that liberates CO very rapidly in solution. Kidneys flushed with Celsior solution supplemented with CO-RMs (50 microM) and stored at 4 degrees C for 24 h displayed at reperfusion a significantly higher perfusion flow rate (PFR), glomerular filtration rate, and sodium and glucose reabsorption rates compared to control kidneys flushed with Celsior solution alone. Addition of 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one (ODQ), a guanylate cyclase inhibitor, prevented the increase in PFR mediated by CO-RMs. The respiratory control index from kidney mitochondria treated with CO-RMs was also markedly increased. Notably, renal protection was lost when kidneys were flushed with Celsior containing an inactive compound (iCO-RM), which had been deliberately depleted of CO. CO-RMs are effective therapeutic agents that deliver CO during kidney cold preservation and can be used to ameliorate vascular activity, energy metabolism and renal function at reperfusion.