摘要:

Abstract—Aminopeptidase N (APN) is an abundant metallohydrolase in the brush border of kidney proximal tubule cells that degrades angiotensin III (Ang III) to angiotensin IV (Ang IV) and, along with dipeptidylaminopeptidase, degrades Ang IV. We examined the impact of a high-salt diet on renal APN activity and transcript abundance in the Sprague-Dawley and Dahl salt-sensitive (SS/Jr) rat strains. APN transcript abundance and protein abundance were ≈2-fold greater (P<0.05; n=6) in the kidneys of Sprague-Dawley and Lewis rats ingesting 8% versus 0.3% salt diets, suggesting that increased aminopeptidase activity may contribute to decreased renal sodium uptake during adaptation to a high-salt diet. In contrast, renal APN transcript abundance and activity were the same in Dahl SS/Jr rats ingesting 8.0% versus 0.3% salt diets. The APN gene was mapped, using a radiation-hybrid panel, to known quantitative loci on chromosome 1 for blood pressure in the Dahl SS/Jr rat. The results suggest that the APN gene is a good candidate for salt-sensitivity in the Dahl SS/Jr rat.

ISSN:0194-911X    

出版商:OVID    

年代:2004

数据来源: OVID

摘要:

Abstract—The present study was designed to determine the capability of human renal proximal tubule (RPT) to generate and export guanosine cyclic 3′, 5′ monophosphate (cGMP) in response to direct stimulation of soluble guanylyl cyclase by nitric oxide (NO) donors. In addition, we investigated whether cGMP extrusion from human RPT cells is required for inhibition of cellular sodium uptake. RPT cells were cultured from fresh human kidneys (normotensive subjects, n=4, mean age 65±4.7 years, 3 men, 1 woman; hypertensive patients, n=6, mean age 64±6.1 years, 4 men, 2 women) after unilateral nephrectomy. The fluorescence dye Sodium Green was employed to determine cytoplasmic Na+concentration. In the presence of the Na+/K+ATPase inhibitor ouabain, fluorescence was monitored at the appropriate wavelength (excitation 485 nm, emission 535 nm). Nitric oxide donor, S-nitroso-N-acetylpenicillamine (SNAP, 10−4M), increased both intracellular and extracellular cGMP (from 1.26±0.21 to 88.7±12.6 pmol/mg protein and from 0.58±0.10 to 9.24±1.9 pmol/mL, respectively,P<0.01) and decreased cellular Na+uptake by 37.4±6.8% (P<0.05) compared with control. The effects of SNAP on cGMP production were similar in normotensive and hypertensive subjects. The increases in intracellular and extracellular cGMP concentration because of SNAP were blocked completely by soluble guanylyl cyclase inhibitor ODQ (1-H-[1,2,4] oxadiazolo [4,2-alpha] quinoxalin-1-one). Probenecid, an organic anion transport inhibitor, augmented the SNAP (10−6M)-induced increase in intracellular cGMP accumulation (from 4.9±0.9 to 9.8±1.5 pmol/mg protein,P<0.05), abrogated the SNAP-induced increase in extracellular cGMP extrusion (from 1.07±0.4 to 0.37±0.1 pmol/L,P<0.05) and blocked the SNAP-induced reduction in cellular Na+uptake. Neither intracellular nor extracellular cGMP were influenced by l-arginine, the metabolic precursor of NO, orNG-nitro-l-arginine methyl ester, an inhibitor of NO synthase. After exogenous administration of cGMP (10−5M) or its membrane-permeable analogue 8-Br-cGMP (10−5M), only 8-Br-cGMP crossed the cell membrane to increase intracellular cGMP (from 1.36±0.19 to 289.7±29.4 pmol/mg protein,P<0.01). However, both cGMP and 8-Br-cGMP were effective in decreasing cellular Na+uptake. In conclusion, human RPT cells contain soluble guanylyl cyclase and are able to generate and export cGMP in response to NO. Because human RPT cells do not themselves contain constitutive NO synthase, the NO-generating cGMP must be derived from sources outside the human RPT. The cGMP cellular export system is critical in the regulation of RPT cellular Na+absorption in humans.

ISSN:0194-911X    

出版商:OVID    

年代:2004

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:2004

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:2004

数据来源: OVID