Iodinated contrast induced renal vasoconstriction is due in part to the downregulation of renal cortical and medullary nitric oxide synthesis.
OBJECTIVE
The loss of renal function continues to be a frequent complication of the iodinated contrast agents used to perform diagnostic angiography and endovascular procedures. This study examined the hypothesis that contrast-induced renal injury is partly due to a decrease in cortical and medullary microvascular blood flow after the downregulation of endogenous renal cortical and medullary nitric oxide (NO) synthesis.


METHODS
Anesthetized male Sprague-Dawley rats (300 g) had microdialysis probes or laser Doppler fibers inserted into the renal cortex to a depth of 2 mm and into the renal medulla to a depth of 4 mm. Laser Doppler blood flow was continuously monitored, and the microdialysis probes were connected to a syringe pump and perfused in vivo at 3 muL/min with lactated Ringer's solution. Dialysate fluid was collected at time zero (basal) and 60 minutes after infusion of either saline or Conray 400 (6 mL/kg). Both groups were treated with saline carrier, N(omega)-nitro-L-arginine methyl ester hydrochloride (L-NAME, 30 mg/kg), L-arginine (400 mg/kg), or superoxide dismutase (10,000 U/kg), an oxygen-derived free radical scavenger. Dialysate was analyzed for total NO and eicosanoid synthesis. The renal cortex and medulla were analyzed for inducible NO synthase (iNOS), cyclooxygenase-2 (COX2), prostacyclin synthase, and prostaglandin E(2) (PGE(2)) synthase content by Western blot analysis.


RESULTS
Conray caused a marked decrease in cortical and medullary blood flow with a concomitant decrease in endogenous cortical NO, PGE(2), and medullary NO synthesis. The addition of L-NAME to the Conray further decreased cortical and medullary blood flow and NO synthesis, which were restored toward control by L-arginine. Neither L-NAME nor L-arginine (added to the Conray) altered cortical or medullary eicosanoids release. Medullary PGE(2) synthesis decreased when superoxide dismutase was added to the Conray treatment, suggesting that oxygen-derived free radicals had a protective role in maintaining endogenous medullary PGE(2) synthesis after Conray treatment. Conray did not significantly alter iNOS, COX-2, prostacyclin synthase, or PGE(2) synthase content.


CONCLUSIONS
These findings suggest that the downregulation of renal cortical and medullary NO synthesis contributes to the contrast-induced loss of renal cortical and medullary microvascular blood flow. Preservation of normal levels of renal cortical and medullary NO synthesis may help prevent or lessen contrast-induced renal vasoconstriction and lessen contrast-induced renal injury found after diagnostic and therapeutic endovascular procedures.
Myers
Stuart I
SI
McGuire Research Institute/McGuire Veterans Administration Medical Center and Department of Surgery, Virginia Commonwealth University, Richmond, VA, USA. simyers1951@aol.com
Wang
Li
L
Liu
Fang
F
Bartula
Lori L
LL
D000818:Animals; D001120:Arginine / Q000494:pharmacology; D003287:Contrast Media / Q000633:toxicity*; D015232:Dinoprostone / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007483:Iothalamic Acid / Q000633:toxicity*; D007672:Kidney Cortex / Q000098:blood supply* / Q000187:drug effects / Q000378:metabolism; D007679:Kidney Medulla / Q000098:blood supply* / Q000187:drug effects / Q000378:metabolism; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation / Q000187:drug effects; D013482:Superoxide Dismutase / Q000494:pharmacology; D014661:Vasoconstriction
D003287:Contrast Media; D004791:Enzyme Inhibitors; D007483:Iothalamic Acid; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D013482:Superoxide Dismutase; D015232:Dinoprostone; D019331:NG-Nitroarginine Methyl Ester