ISSN:
1432-0428
Keywords:
Key words Na+/H+ exchanger
;
endothelial cells
;
cell replication
;
fibronectin
;
diabetic nephropathy.
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary 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 (Δ = –0.98 ± 0.93 nmol · mg protein–1· min–1 p 〈 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. [Diabetologia (1995) 38: 785–791]
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s001250050353
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