Gentamicin causes endocytosis of Na/Pi cotransporter protein (NaPi-2)

V. Sorribas, N. Halaihel, K. Puttaparthi, T. Rogers, R. E. Cronin, A. I. Alcalde, J. Aramayona, M. Sarasa, H. Wang, P. Wilson, H. Zajicek, M. Levi

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13 Scopus citations

Abstract

Background. Renal toxicity is a major side-effect of aminoglycoside antibiotics and is characterized by an early impairment in proximal tubular function. In a previous study, we have shown that gentamicin administration to the rat causes an early impairment in sodium gradient-dependent phosphate (Na/Pi) cotransport activity. The purpose of our current study was to determine the molecular mechanisms of the impairment in Na/pi cotransport activity, specifically the role of the proximal tubular type II Na/Pi cotransporter. Methods. Rats were treated for one, two, and three days with two daily injections of 30 mg/kg body weight gentamicin or the vehicle. Results. Gentamicin caused a progressive decrease in superficial cortical apical brush-border membrane (SC-BBM) Na/Pi cotransporter activity (856 ± 93 in control vs. 545 ± 87 pmol/mg BBM protein in 3-day gentamicin, P < 0.01). Western blot analysis showed a parallel and progressive decrease in SC-BBM Na/Pi cotransporter protein abundance, a 50% decrease after one day of treatment, a 63% decrease after two days of treatment, and an 83% decrease after three days treatment with gentamicin. In contrast, gentamicin treatment had no effect on Na/Pi cotransport activity or Na/Pi cotransporter protein abundance in BBM isolated from the juxtamedullary cortex (JMC-BBM). Immunofluorescence microscopy showed a major decrease in the expression of Na/Pi cotransporter protein in the apical membrane of the proximal convoluted tubule, with progressive intracellular accumulation of Na/Pi protein. Colocalization studies showed that in gentamicin-treated rats, Na/Pi protein was colocalized in the early endosomes and especially in the lysosomes. Northern blot analysis of cortical RNA interestingly showed no reduction in Na/Pi cotransporter mRNA abundance even after three days of gentamicin treatment. Conclusion. We conclude that gentamicin inhibits Na/Pi cotransport activity by causing a decrease in the expression of the type II Na/Pi cotransport protein at the level of the proximal tubular apical BBM and that inhibition of Na/Pi cotransport activity is most likely mediated by post-transcriptional mechanisms.

Original languageEnglish (US)
Pages (from-to)1024-1036
Number of pages13
JournalKidney international
Volume59
Issue number3
DOIs
StatePublished - Jan 1 2001

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Keywords

  • Axial hetergeneity
  • Early endosomes
  • Lysosomes
  • Nephrotoxicity
  • Phosphatidylinositol
  • Renal toxicity
  • Type II Na/pi cotransport activity

ASJC Scopus subject areas

  • Nephrology

Cite this

Sorribas, V., Halaihel, N., Puttaparthi, K., Rogers, T., Cronin, R. E., Alcalde, A. I., Aramayona, J., Sarasa, M., Wang, H., Wilson, P., Zajicek, H., & Levi, M. (2001). Gentamicin causes endocytosis of Na/Pi cotransporter protein (NaPi-2). Kidney international, 59(3), 1024-1036. https://doi.org/10.1046/j.1523-1755.2001.0590031024.x