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 foun d that incubation of renal tissue homogenate with the O-2(-). donor KO2 dou bled 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 sy stem, xanthine/xanthine oxidase increased the maximal reaction velocity of 5'-ND from 122 to 204 nmol.min(-1).mg protein(-1). Superoxide dismutase (SO D) with catalase produced a concentration-dependent reduction of 5'-ND acti vity in renal tissue homogenate, while the SOD inhibitor diethyldithiocarba mic acid significantly increased 5'-ND activity. Inhibition of disulfide bo nd formation by thioredoxin or thioredoxin reductase significantly decrease d xanthine/xanthine oxidase-induced activation of renal 5'-ND. In in vivo e xperiments, inhibition of SOD by diethyldithiocarbamic acid (0.5 mg.kg(-1). min(-1) iv) enhanced renal vasoconstriction induced by endogenously produce d adenosine and increased renal tissue adenosine concentrations under contr ol condition and in ischemia and reperfusion. We conclude that oxidative st ress activates 5'-ND and increases adenosine production in the kidney and t hat this redox regulatory mechanism of adenosine production is important in the control of renal vascular tone and glomerular perfusion.