Ecto-5’-Nucleotidase of Cultured Rat Mesangial Cells
作者:
Vladisav Stefanovic,
Vojin Savic,
Predrag Vlahovic,
Nicole Ardaillou,
Raymond Ardaillou,
期刊:
Kidney and Blood Pressure Research
(Karger Available online 1988)
卷期:
Volume 11,
issue 1-2
页码: 89-102
ISSN:1420-4096
年代: 1988
DOI:10.1159/000173153
出版商: S. Karger AG
关键词: 5’-Nucleotidase;Ectoenzymes;Mesangial cells;Glomerulus;Adenosine
数据来源: Karger
摘要:
Because adenosine plays a role in the regulation of glomerular filtration rate and of the release of renin, we examined the possibility of a local source for this mediator. We found that rat cultured glomerular mesangial cells converted 5’-AMP into adenosine. The properties of the enzyme involved in the reaction were those of an ecto-5’nucleotidase: (1) the products of the reaction were generated in the extracellular fluid although no 5’-nucleotidase was released by the cells into the medium; (2) identical activities were found for cultured cells in situ and sonicated cells; (3) the diazonium salt of sulfanilic acid which is a nonpenetrating reagent inhibited up to 75% of the enzyme activity. Ecto-5’-nucleotidase activity of intact cells obeyed Michaelis-Menten kinetics. Apparent Km for 5’-AMP was 0.32 mM. 5’-UMP was a strictly competitive inhibitor. ADP exerted a very powerful inhibitory effect and behaved also as a competitive inhibitor. ATP was inhibitory both by increasing Km and by decreasing Vmax. Ecto-5’-nucleotidase was active in the absence of divalent cations. However, Mg2+, Ca2+, Co2+ and Mn2+ were stimulatory. Zn2+ and Cu2+ suppressed the activity. Concanavalin A, a plant lectin, was markedly inhibitory, suggesting that a glycoprotein moiety was necessary to express enzyme activity. Ecto-5’-nucleotidase activity was not modified during phagocytosis of serum-treated zymosan by mesangial cells. Rat cultured glomerular epithelial cells exhibited a 5’-nucleotidase activity which was 4 times lower than that of the mesangial cells in primary culture. Activity was also present in freshly isolated glomeruli and total cortex, but at lower concentrations than in mesangial cells. These findings suggest that ecto-5’-nucleotidase of mesangial cells may be the main source of adenosine within the glomeruli. Therefore, activity of this enzyme should be essential in the regulation of the glomerul
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