Temperature-dependent differences between readily releasable and reserve pool vesicles in chromaffin cells

Christy L. Haynes, Lauren N. Siff, R. Mark Wightman

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35 Scopus citations


Statistical differences between amperometric traces recorded from chromaffin cells using K+ and Ba2+ secretagogues support the assertion that readily releasable pool (RRP) and reserve pool (RP) vesicles can be probed with pool-specific secretagogues. Release from the RRP was evoked by K+ while release from the RP was evoked by Ba2+. Similar temperature-dependent changes in spike area and half-width for both pools suggest that the content of RRP and RP vesicles is similar and packaged in the same way. Differences between the vesicle pools were revealed in the temperature dependence of spike frequency. While the burst spike frequency of the RRP, which is comprised of pre-docked and primed vesicles, increased 2.8% per °C, the RP spike frequency increased 12% per °C. This difference is attributed to a temperature-dependent mobilization of the RP. Furthermore, the RP exhibited more foot events at room temperature than the RRP but this difference was not apparent at 37 °C. This trend suggests that RP vesicle membranes have a compromised surface tension compared to RRP vesicles. Collectively, the changes of release characteristics with temperature reveal distinctions between the RRP and the RP.

Original languageEnglish (US)
Pages (from-to)728-735
Number of pages8
JournalBiochimica et Biophysica Acta - Molecular Cell Research
Issue number6
StatePublished - Jun 2007

Bibliographical note

Funding Information:
We thank Dr. Leslie A. Sombers for assistance in data analysis and Melissa Villanueva for assistance with the cell culture. This work was funded by the National Institutes of Health (NS 38879) and a Ruth L. Kirschstein National Research Service Award to C. L. H.


  • Amperometry
  • Carbon-fiber microelectrode
  • Catecholamine
  • Exocytosis
  • Vesicle pools


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