Activity and expression of the Na+/H+ exchanger in human endothelial cells cultured in high glucose

G. Zerbini, T. Roth, E. Podestá, E. Cagliero, A. Doria, M. Canessa, M. Lorenzi

Research output: Contribution to journalArticle

Abstract

Establishing whether high ambient glucose affects the plasma membrane Na+/H+ exchanger is relevant to understanding the adverse effects of high glucose on cell replication and the mechanisms of the increased exchanger activity encountered in diabetic patients with nephropathy. In 8 primary and 15 first-passage isolates of human endothelial cells cultured in 30 mmol/l glucose for 8.7±2.3 and 15.8±2.3 days, respectively, we determined Na+/H+ exchanger activity and mRNA levels. Activity was determined by measuring 22Na+ influx in the presence or absence of dimethylamiloride (DMA) after intracellular acidification. We also measured fibronectin mRNA because fibronectin provides signals for cell replication through the Na+/H+ antiporter. Control cells grown in 5 mmol/l glucose showed at morphologic confluency a total Na+ influx (in nmol · mg protein-1 · min-1) of 10.1±3.2 in primary and 11.7±2.2 in first subculture, which was reduced to 5.3±0.3 in the presence of DMA. Paired cultures exposed to 30 mmol/l glucose and exhibiting pHi and cell densities identical to controls showed in both primary and first subculture a reduction in total Na+ influx (A = -0.98±0.93 nmol · mg protein-1 · min-1p <0.005) whereas DMA-resistant Na+ influx was identical to that of control. Neither chronic hypertonicity nor acute exposure to high glucose mimicked the effects of chronic high glucose. The level of the Na+/H+ exchanger isoform 1 (NHE-1) mRNA was unchanged by high glucose whereas fibronectin mRNA levels were increased 1.5-fold. These studies indicate that in endothelial cells exposed to elevated ambient glucose the regulation of the Na+/H+ exchanger is altered at the post-transcriptional level; decreased activity of the antiporter is concomitant with fibronectin overexpression and may contribute to the decreased replication caused by high glucose.

Original languageEnglish
Pages (from-to)785-791
Number of pages7
JournalDiabetologia
Volume38
Issue number7
DOIs
Publication statusPublished - Jul 1995

Keywords

  • cell replication
  • diabetic nephropathy
  • endothelial cells
  • fibronectin
  • Na/H exchanger

ASJC Scopus subject areas

  • Internal Medicine
  • Endocrinology, Diabetes and Metabolism

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