Nitric oxide in afferent arterioles after uninephrectomy depends on extracellular L-arginine.

Frank Helle, Trude Skogstrand, Idit F Schwartz, Doron Schwartz, Bjarne M Iversen, Fredrik Palm, Michael Hultström

Renal Research Group, Institute of Medicine, University of Bergen, Bergen, Norway.

American journal of physiology. Renal physiology 2013 Apr 15

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Uninephrectomy (UNX) causes hyperperfusion of the contralateral remaining kidney via increased nitric oxide (NO) synthesis. Although the exact mechanism remains largely unknown, we hypothesize that this would be localized to the afferent arteriole and that it depends on cellular uptake of l-arginine. The experiments were performed in rats 2 days (early) or 6 wk (late) after UNX and compared with controls (Sham) to study acute and chronic effects on NO metabolism. Renal blood flow was increased after UNX (21 ± 2 ml·min(-1)·kg(-1) in sham, 30 ± 3 in early, and 26 ± 1 in late, P < 0.05). NO inhibition with N(ω)-nitro-L-arginine methyl este r hydrochloride (L-NAME) caused a greater increase in renal vascular resistance in early UNX compared with Sham and late UNX (138 ± 24 vs. 88 ± 10, and 84 ± 7%, P < 0.01). The lower limit of autoregulation was increased both in early and late UNX compared with Sham (P < 0.05). L-NAME did not affect the ANG II-induced contraction of isolated afferent arterioles (AA) from Sham. AA from early UNX displayed a more pronounced contraction in response to L-NAME (-57 ± 7 vs. -16 ± 7%, P < 0.05) and in the absence of L-arginine (-41 ± 4%, P < 0.05) compared with both late UNX and Sham. mRNA expression of endothelial NO synthase was reduced, whereas protein expression was unchanged. Cationic amino acid transporter-1 and -2 mRNA was increased, while protein was unaffected in isolated preglomerular resistance vessels. In conclusion, NO-dependent hyperperfusion of the remaining kidney in early UNX is associated with increased NO release from the afferent arteriole, which is highly dependent on extracellular L-arginine availability.

Citation

Frank Helle, Trude Skogstrand, Idit F Schwartz, Doron Schwartz, Bjarne M Iversen, Fredrik Palm, Michael Hultström. Nitric oxide in afferent arterioles after uninephrectomy depends on extracellular L-arginine. American journal of physiology. Renal physiology. 2013 Apr 15;304(8):F1088-98