[Ca 2+ ](i) and pH(in) homeostasis in Kaposi sarcoma cells

Raul Martínez-Zaguilán, Brian F. Chinnock, Sarah Wald-Hopkins, Mike Bernas, Dennis Way, Martin Weinand, Marlys H. Witte, Robert J. Gillies

Research output: Contribution to journalArticlepeer-review

35 Scopus citations

Abstract

Changes in intracellular pH (pH(in)) and intracellular calcium concentration [Ca 2+ ](i) play a major role in signal transduction leading to cell growth, differentiation and transformation. In some tumor cell lines, vacuolar (V-type) H + -adenosine triphosphatases (ATPases) are important in pH(in) regulation. To clarify the neoplastic nature and endothelial origin of Kaposi sarcoma (KS), pH(in) and [Ca 2+ ](i) and the functional expression of V-type H + -ATPases were evaluated in cultured endothelial marker-positive KS cells derived from AIDS-KS skin lesions as compared to human umbilical vein endothelial cells (HUVEC). Human skin fibroblasts (HSF) were also examined. Cells were examined using fluorescence spectroscopy with the pH(in) indicator SNARF-1 and the [Ca 2+ ](i) indicator Fura-2. We found that whereas pH(in) recovery from acid loading occurred in the absence of Na + and HCO 3 - in HUVEC and HSF, KS cells did not recover. Moreover, removal of extracellular Na + had no effect on [Ca 2+ ](i) in HUVEC, but transiently increased [Ca 2+ ](i) in KS cells and HSF. This [Ca 2+ ](i) spike was unaffected by Ca 2+ -free medium, suggesting that it is not due to Na + /Ca 2+ exchange. In addition, use of K + -containing and K + -free medium to mimic depolarization or hyperpolarization, which may occur during Na + removal, did not cause [Ca 2+ ](i) changes. The [Ca 2+ ](i) levels were also not sensitive to intracellular acidification but were specifically sensitive to [Na + ]. Thus, KS cells differ from normal endothelial cells in the kinetics of pH(in) recovery to acid loads, and in the presence of a specific [Na + ]-sensitive intracellular Ca 2+ pool. These differences in ion homeostasis indicate that these cell types are not developmentally related or that alterations in ion transport are a part of the etiology of the KS lesion.

Original languageEnglish (US)
Pages (from-to)169-184
Number of pages16
JournalCellular Physiology and Biochemistry
Volume6
Issue number3
StatePublished - Jan 1 1996

Keywords

  • Endothelial cells
  • Fluorescence
  • Fura-2
  • Human skin fibroblasts
  • Kaposi sarcoma
  • Na /Ca exchange
  • Na /H exchange
  • SNARF-1
  • [Ca ](i)
  • pH(in)

ASJC Scopus subject areas

  • Physiology

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