Dynamics of Ca2+i and pHi in Ehrlich ascites tumor cells after Ca2+-mobilizing agonists or exposure to hypertonic solution

Pflugers Arch. 1998 Jul;436(2):199-210. doi: 10.1007/s004240050623.

Abstract

Intracellular free calcium concentration ([Ca2+]i) and intracellular pH (pHi) were monitored in Ehrlich ascites tumor cells using Fura-2 or 2',7',-bis-(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF), or both probes in combination. An increase in [Ca2+]i induced by thrombin or bradykinin, agonists known to elicit transient cell shrinkage in these cells, evoked a transient intracellular acidification, followed by an alkalinization. The latter was due to activation of a Na+/H+ exchanger and was inhibited under conditions preventing agonist-induced cell shrinkage without preventing the increase in [Ca2+]i. In contrast, a smaller, slower increase in [Ca2+]i elicited by thapsigargin did not cause cell shrinkage, and did not activate the Na+/H+ exchanger. Exposure to hypertonic solution was not associated with an increase in [Ca2+]i, but elicited an intracellular alkalinization similar to that induced by thrombin or bradykinin, via activation of the Na+/H+ exchanger. Thus, activation of the exchanger by the Ca2+-mobilizing agonists is suggested to be secondary to the cell shrinkage induced by these compounds. NH4Cl-induced intracellular alkalinization resulted in an increase in [Ca2+]i, apparently via stimulation of Ca2+ influx, whereas shrinkage-induced intracellular alkalinization did not stimulate Ca2+ influx. Thus, cell shrinkage appears to inhibit the Ca2+ influx otherwise resulting from alkalosis. In agreement with that notion, thapsigargin-induced Ca2+ influx was inhibited by cell shrinkage.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ammonium Chloride / pharmacology
  • Animals
  • Bradykinin / pharmacology*
  • Calcium / metabolism*
  • Carcinoma, Ehrlich Tumor / metabolism*
  • Cell Size
  • Fluoresceins
  • Fluorescent Dyes
  • Fura-2
  • Hydrogen-Ion Concentration
  • Hypertonic Solutions*
  • Sodium-Hydrogen Exchangers / physiology
  • Thapsigargin / pharmacology
  • Thrombin / pharmacology*

Substances

  • Fluoresceins
  • Fluorescent Dyes
  • Hypertonic Solutions
  • Sodium-Hydrogen Exchangers
  • Ammonium Chloride
  • Thapsigargin
  • 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein
  • Thrombin
  • Bradykinin
  • Calcium
  • Fura-2