Three distinct K$ sp+$ currents were identified in corn (Zea mays) protoplasts using the whole-cell patch-clamp technique. Inward-rectifying K$ sp+$ currents were evoked at membrane potentials more negative than $-$100 mV. The activation range was sensitive to external K$ sp+$ and shifted in the positive direction as the K$ sp+$ concentration was elevated. The second K$ sp+$ current was voltage-independent and contributed to the resting membrane conductance of the protoplast. Finally, a voltage- and Ca$ sp{2+}$-dependent K$ sp+$ current was observed at potentials positive to $-$60 mV. This current was inhibited by reagents which antagonize plasmalemma Ca$ sp{2+}$ influx (e.g. nitrendipine, verapamil). In contrast, currents were enhanced by increasing the cytosolic free Ca$ sp{2+}$ concentration from 40 to 400 nM. The Ca$ sp{2+}$-dependent K$ sp+$ current was inhibited by tetraethylammonium ions, Cs$ sp+$, Ba$ sp{2+}$, and charybdotoxin which suggested that the channel protein has structural similarities to the high conductance Ca$ sp{2+}$-dependent K$ sp+$ channel observed in animal systems.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.74658 |
| Date | January 1990 |
| Creators | Ketchum, Karen Ann |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001236477, proquestno: AAINN67770, Theses scanned by UMI/ProQuest. |
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