Arginine transport is augmented, through modulation of cationic amino acid transporter-1, in obstructive uropathy in rats.

BACKGROUND: The decrease in glomerular filtration rate (GFR), which is characteristic of obstructive uropathy, was suggested to be associated with attenuated nitric oxide (NO) generation. Since availability of L-arginine, the sole precursor for NO, governs NO synthesis, we aimed to determine the role of glomerular arginine transport in rats subjected to 24 h of bilateral ureteral ligation (BUO). METHODS: Glomerular arginine transport was measured by uptake of radiolabeled arginine ([(3)H]-L-arginine), cationic amino acid transporters (CAT)-1 and -2 and arginases I and II mRNA expression were determined using reverse transcription-polymerase chain reaction. CAT-1, arginase I, and arginase II protein contents were evaluated by Western blotting. RESULTS: L-Arginine transport by freshly harvested glomeruli from BUO rats was significantly augmented than in controls. The aforementioned findings were associated with a significant increase in glomerular CAT-1 mRNA expression, while CAT-2 mRNA was unchanged. Western blotting demonstrated a significant increase in CAT-1 abundance in BUO. Expression of both glomerular arginase I and II mRNA and protein content were significantly elevated in BUO. CONCLUSIONS: BUO induces an increase in glomerular arginine transport via upregulation of CAT-1, probably due to increase in arginine utilization by a non-NO pathway.

Heart valve calcification in young patients with systemic lupus erythematosus: a window to premature atherosclerotic vascular morbidity and a risk factor for all-cause mortality.

The objective of the study was to evaluate the association between heart valve calcification and atherosclerosis and outcome in systemic lupus erythematosus (SLE). One-hundred and seven patients with SLE (mean age 45.9 +/- 14.7 years) were studied by 2D transthoracic echocardiography. Mitral annulus calcification (MAC) was detected in 24 patients (22.6%) and aortic valve calcification (AVC) in 22 (20.1%). Both MAC and AVC were associated with older age (r = 0.2, p = 0.02; r = 0.40, p

Rosiglitazone improves aortic arginine transport, through inhibition of PKCalpha, in uremic rats.

Peroxisome proliferator-activated receptor (PPAR) agonists were shown to inhibit atherosclerosis through augmentation of endothelial nitric oxide synthase (eNOS) activity. In addition, rosiglitazone exerts a beneficial effect in chronic renal failure (CRF). Since l-arginine transport by CAT-1 (the specific arginine transporter for eNOS) is inhibited in uremia, we aimed to explore the effect of rosiglitazone on arginine transport in CRF. Arginine uptake by aortic rings was studied in control animals, rats, 6 wk following 5/6 nephrectomy (CRF) and rats with CRF treated with rosiglitazone. The decrease of arginine transport in CRF was prevented by rosiglitazone. Immunobloting revealed that CAT-1 protein was decreased in CRF but remained unchanged following rosiglitazone administration. Protein content of the membrane fraction of PKCalpha and phosphorylated CAT-1 increased significantly in CRF, effects that were prevented by rosiglitazone. PKCalpha phosphorylation was unchanged but significantly attenuated by rosiglitazone in CRF. Ex vivo administration of phorbol-12-myristate-13-acetate to rosiglitazone-treated CRF rats significantly attenuated the effect of rosiglitazone on arginine uptake. The decrease in cGMP response to carbamyl-choline (eNOS agonist) was significantly attenuated by rosiglitazone in CRF. Western blotting and immunohistochemistry analysis revealed that protein nitration was intensified in the endothelium of CRF rats and this was attenuated by rosiglitazone. In conclusion, rosiglitazone prevents the decrease in arginine uptake in CRF through both depletion and inactivation of PKCalpha. These findings are associated with restoration of eNO generation and attenuation of protein nitration and therefore may serve as a novel mechanism to explain the beneficial effects of rosiglitazone on endothelial function in uremia.