Temperature-Dependent Differences Between Readily Releasable and Reserve Pool Vesicles in Chromaffin Cells (2007)

Undergraduate: Lauren Siff

Faculty Advisor: R. Mark Wightman
Department: Chemistry

---

Differences between readily releasable pool (RRP) and reserve pool (RP) vesicles were probed with pool-specific secretagogues while measuring the temperature dependence of release with amperometry. 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 spike frequency of the RRP, which is comprised of pre-docked and primed vesicles, was independent of temperature, the RP spike frequency increased with temperature. This difference is attributed to a temperature dependent mobilization of the RP. Furthermore, the RP exhibited more fusion pore events at room temperature than the RRP but this difference was not apparent at 37?C. This feature indicates sub-optimal ATP-dependent priming or Ca2+-dependent fusion for some RP vesicles at room temperature. Collectively, the changes of release characteristics with temperature reveal distinctions between the RRP and the RP.