The influence of acute renal injury on arginine and methylarginines metabolism

Arginine (ARG) and its methylated analogs (methylarginines) are the crucial regulators of nitric oxide (NO) bioavailability. ARG is the substrate for NO synthesis, whereas monomethylarginine (MMA) and asymmetric dimethylarginine (ADMA) are potent inhibitors. Symmetric dimethylarginine (SDMA) does not interfere with NO synthesis, but competes with ARG for the intracellular transport. The kidneys play the major role in ARG and methylarginines metabolism. They synthesize ARG de novo and eliminate methylarginines by excretion into urine and also by enzyme dimethylarginine dimethylaminohydrolase (DDAH) degrading only ADMA and MMA. Acute renal injury (ARI) is known to be accompanied by reduced NO production in the body. This study aimed to investigate the influence of ARI on ARG and methylarginines metabolism, and to establish the relationship between disturbances in the latter and reduced NO bioavailability in ARI. The rhabdomyolysis-related ARI model in rats was used. ARI reduced renal synthesis of ARG and its level in circulation as well as renal DDAH activity. However, ADMA did not accumulate because of its increased urinary excretion. Whole-body production of SDMA was increased significantly, whereas whole-body metabolism of MMA did not change. ARG and methylarginines content in renal tissue was decreased. Moreover, the balance between the substrate and inhibitors for NO synthesis was changed in favor of the inhibitors in renal tissue as well as in blood, and daily urinary excretion of NO metabolites was significantly decreased. Thus, ARI provokes severe disturbances in ARG and methylarginines metabolism that results in reduced NO bioavailability in the kidney and the whole body.