Oxidative stress enhances the production and actions of adenosine in the kidney

The purpose of this study was to determine whether superoxide anions (O-2(-).) activate 5'-nucleotidase (5'-ND), thereby increasing the production of renal adenosine and regulating renal function. Using HPLC analysis, we found that incubation of renal tissue homogenate with the O-2(-). donor KO2 doubled adenosine production and increased the maximal reaction velocity of 5'-ND from 141 to 192 nmol.min(-1).mg protein(-1). The O-2(-). -generating system, xanthine/xanthine oxidase increased the maximal reaction velocity of 5'-ND from 122 to 204 nmol.min(-1).mg protein(-1). Superoxide dismutase (SOD) with catalase produced a concentration-dependent reduction of 5'-ND activity in renal tissue homogenate, while the SOD inhibitor diethyldithiocarbamic acid significantly increased 5'-ND activity. Inhibition of disulfide bond formation by thioredoxin or thioredoxin reductase significantly decreased xanthine/xanthine oxidase-induced activation of renal 5'-ND. In in vivo experiments, inhibition of SOD by diethyldithiocarbamic acid (0.5 mg.kg(-1).min(-1) iv) enhanced renal vasoconstriction induced by endogenously produced adenosine and increased renal tissue adenosine concentrations under control condition and in ischemia and reperfusion. We conclude that oxidative stress activates 5'-ND and increases adenosine production in the kidney and that this redox regulatory mechanism of adenosine production is important in the control of renal vascular tone and glomerular perfusion.