Arginine and asymmetric dimethylarginine in puromycin aminonucleoside-induced chronic kidney disease in the rat.

BACKGROUND/AIMS: Reduced renal L-arginine (L-Arg) synthesis/transport, induction of arginases and increased endogenous NOS inhibitor, asymmetric dimethylarginine (ADMA) will inhibit NO production. This study investigated pathways of L-Arg synthesis/uptake/utilization, ADMA degradation and oxidant/antioxidants in puromycin aminonucleoside (PAN) chronic kidney disease (CKD). METHODS: Rats were given low- (LD) or high-dose (HD) PAN and followed for 11 weeks for proteinuria. BP was measured and blood and tissues were harvested and analyzed for abundance of argininosuccinate synthase (ASS) and lyase (ASL), arginase, cationic amino acid transporter (CAT1) and dimethylargininedimethylaminohydrolase (DDAH) in kidney, cortex, aorta and liver. Arginase and DDAH activity, plasma L-Arg and ADMA, renal pathology and creatinine clearances were also measured. RESULTS: PAN caused dose-dependent kidney damage and hypertension and creatinine clearance fell in HD-PAN. Renal ASS fell in HD-PAN, renal cortex and aortic ASL and membrane CAT1 fell in both PAN groups. There was no activation of renal arginase, but aortic arginase increased in LD-PAN. Renal DDAH activity fell moderately in LD-PAN and markedly in HD-PAN where hepatic DDAH activity also fell. Plasma L-Arg was unchanged while ADMA rose moderately and dose-dependently with PAN. There were several indices of oxidative stress which was most prominent in HD-PAN. CONCLUSION: Reduction in renal ASS/ASL and loss of renal cortex CAT1 compromises renal L-Arg synthesis and release. Loss of aortic CAT1 impairs L-Arg uptake. Increased plasma ADMA was associated with progressive loss of renal DDAH activity. However, loss of renal clearance and falls in hepatic DDAH activity in HD-PAN did not have additive effects on plasma ADMA.

Glomerular arginine transport is attenuated in chronic renal failure in rats.

UNLABELLED: L-Arginine supplementation was found to have a reno-protective effect in different models of chronic renal failure (CRF) in spite of normal plasma levels. Experiments were designed to determine if changes in glomerular uptake of arginine occur in 5/6 nephrectomized rats as a model of CRF. Renal function and glomerular uptake of radiolabeled arginine {[3H] L-arginine} was measured in sham operated, 5/6 nephrectomy, and right nephrectomy rats. Renal failure and proteinuria was found in the CRF animals only. Arginine uptake by glomeruli harvested from rats with CRF was significantly lower than that by glomeruli from sham operated and unilateral nephrectomy rats. IN CONCLUSION: glomerular arginine uptake is decreased in CRF. This phenomenon can explain the beneficial effect of L-arginine supplementation in CRF.

Garlic attenuates nitric oxide production in rat cardiac myocytes through inhibition of inducible nitric oxide synthase and the arginine transporter CAT-2 (cationic amino acid transporter-2).

It is now accepted that allicin, the main biologically active compound in garlic, exhibits antioxidant activity. The present study was designed to test the hypothesis that the antioxidant activity of garlic can be partially attributed to the inhibition of nitric oxide (NO) production by cytokine-induced NO synthase (iNOS). Cardiac myocytes cultured from neonatal Wistar rats were stimulated by lipopolysaccharide (LPS) and incubated for 24 h with various concentrations of allicin. This resulted in marked inhibition of nitrite production. Interestingly, a low concentration of allicin (10 microM) was significantly more potent in abrogating the effect of LPS on nitrite production than a higher concentration (40 microM). Allicin decreased steady-state iNOS mRNA levels, and this effect was maximal when a lower concentration was used (10 microM compared with 40 microM). In order to explore additional effects of allicin on NO generation that might counteract the effect on iNOS, we assessed the effects of higher allicin concentrations on arginine transport. Allicin inhibited the uptake of 1 mM extracellular arginine in a concentration-dependent manner. The expression of the two arginine transporters that are expressed in cardiac myocytes [CAT-1 (cationic amino acid transporter-1) and CAT-2] was studied using reverse transcription-PCR. A concentration of 200 microM allicin abolished the expression of CAT-2 mRNA, 100 microM significantly attenuated it, whereas 50 microM had no effect. Allicin had no effect on steady-state CAT-1 mRNA levels. Our results suggest that allicin inhibits iNOS activity through two different mechanisms: at lower concentrations it decreases iNOS mRNA levels, whereas at higher concentrations it inhibits arginine transport through down-regulation of CAT-2 mRNA.