Differences in the functional responses of two cell lines each expressing Pi-hydrolysis-coupled muscarinic receptors

Neurochem Res. 1992 Apr;17(4):375-9. doi: 10.1007/BF00974580.

Abstract

Fluorescent oxonol dyes were used to measure changes in the membrane potential of two different cell lines each expressing Pi-hydrolysis coupled muscarinic receptors. Both SK-N-SH human neuroblastoma cells and m1-transfected A9 L cells express muscarinic receptors which, when stimulated, elicit a large increase in intracellular calcium, and release of inositol phosphates. Despite the similarity in this second-messenger response, muscarinic stimulation resulted in a hyperpolarization in the transfected A9 L cells whereas a small depolarization was observed in the neuroblastoma cells. The carbachol-mediated hyperpolarization of the transfected A9 L cells could be mimicked by increasing intracellular calcium with the ionophore A23187, suggesting that it may be mediated by calcium-activated potassium channels. Exposure of SK-N-SH cells to A23187, on the other hand, had no effect on the membrane potential. These studies demonstrate that the activation of a second messenger system does not solely dictate the electrophysiological response of a cell, but that other factors such as the expression of ion-channels is critical in the determination of that response.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Calcium / metabolism
  • Cell Line
  • Fluorescent Dyes
  • Fura-2 / analogs & derivatives
  • Humans
  • Hydrolysis
  • Isoxazoles
  • Membrane Potentials / physiology
  • Protein Kinase C / physiology
  • Receptors, Muscarinic / metabolism*
  • Tumor Cells, Cultured

Substances

  • Fluorescent Dyes
  • Isoxazoles
  • Receptors, Muscarinic
  • oxonol dyes (isoxazole)
  • fura-2-am
  • Protein Kinase C
  • Calcium
  • Fura-2