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Kinetics of release of serotonin from isolated secretory granules. II. Ion exchange determines the diffusivity of serotonin.

Publication ,  Journal Article
Marszalek, PE; Farrell, B; Verdugo, P; Fernandez, JM
Published in: Biophysical journal
September 1997

We measured the efflux of 5-hydroxytryptamine (5-HT, serotonin) from an intact secretory granule extracted from the mast cell of the beige mouse. The efflux was measured with amperometry after rupture of the granule membrane was triggered by electroporation. We determined the diffusivity of 5-HT within the secretory granule to be 2.0 x 10(-8) cm2 s(-1) when the granule is in contact with a physiological saline and found that this diffusivity depends on the valence of the cation in the external electrolyte. There is a fivefold increase in the diffusion coefficient of 5-HT determined in CsCl (150 mM, pH 7.2) at 3.7 x 10(-8) cm2 s(-1) compared to that determined in histamine dihydrochloride (Hi, 100 mM at pH 4.5) at 0.7 x 10(-8) cm2 s(-1). We found that the rate of expansion of the granule matrix observed in physiological medium correlates with the efflux of 5-HT, and that the rate of swelling of the matrix and the efflux depend on the microviscosity within the granule matrix and not the bulk viscosity of the external solution. The low diffusivity of 5-HT (approximately 500-fold less than in the bulk), the observation that the valence of the counterion affects this diffusivity, and the relationship between the volume changes of the matrix and the efflux suggest that 5-HT is released from the granule by ion exchange. We discuss the implications of this result for exocytotic release in mast cells and propose that an ion exchange mechanism could control the rate of release in other secretory systems.

Duke Scholars

Published In

Biophysical journal

DOI

EISSN

1542-0086

ISSN

0006-3495

Publication Date

September 1997

Volume

73

Issue

3

Start / End Page

1169 / 1183

Related Subject Headings

  • Viscosity
  • Serotonin
  • Regression Analysis
  • Monte Carlo Method
  • Models, Biological
  • Mice, Inbred Strains
  • Mice
  • Mast Cells
  • Kinetics
  • Hydrogen-Ion Concentration
 

Citation

APA
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MLA
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Marszalek, P. E., Farrell, B., Verdugo, P., & Fernandez, J. M. (1997). Kinetics of release of serotonin from isolated secretory granules. II. Ion exchange determines the diffusivity of serotonin. Biophysical Journal, 73(3), 1169–1183. https://doi.org/10.1016/s0006-3495(97)78149-9
Marszalek, P. E., B. Farrell, P. Verdugo, and J. M. Fernandez. “Kinetics of release of serotonin from isolated secretory granules. II. Ion exchange determines the diffusivity of serotonin.Biophysical Journal 73, no. 3 (September 1997): 1169–83. https://doi.org/10.1016/s0006-3495(97)78149-9.
Marszalek PE, Farrell B, Verdugo P, Fernandez JM. Kinetics of release of serotonin from isolated secretory granules. II. Ion exchange determines the diffusivity of serotonin. Biophysical journal. 1997 Sep;73(3):1169–83.
Marszalek, P. E., et al. “Kinetics of release of serotonin from isolated secretory granules. II. Ion exchange determines the diffusivity of serotonin.Biophysical Journal, vol. 73, no. 3, Sept. 1997, pp. 1169–83. Epmc, doi:10.1016/s0006-3495(97)78149-9.
Marszalek PE, Farrell B, Verdugo P, Fernandez JM. Kinetics of release of serotonin from isolated secretory granules. II. Ion exchange determines the diffusivity of serotonin. Biophysical journal. 1997 Sep;73(3):1169–1183.
Journal cover image

Published In

Biophysical journal

DOI

EISSN

1542-0086

ISSN

0006-3495

Publication Date

September 1997

Volume

73

Issue

3

Start / End Page

1169 / 1183

Related Subject Headings

  • Viscosity
  • Serotonin
  • Regression Analysis
  • Monte Carlo Method
  • Models, Biological
  • Mice, Inbred Strains
  • Mice
  • Mast Cells
  • Kinetics
  • Hydrogen-Ion Concentration