Recent studies have shown that a variety of K$ sp+$ channels can be enhanced by somatostatin (SST; inward and delayed rectifier, muscarinic regulated K$ sp+$ channel, Ca$ sp{2+}$-activated K$ sp+$ channel, ...). Since a somatostatin receptor (SSTR) is heterogeneous, it is not clear which SSTR subtype (five are identified) is involved in regulating each K$ sp+$ channel, nor whether the regulation is and if so to what extent receptor subtype specific. In this study we characterized electrophysiologically the effect of somatostatin-14 (SST-14) in monkey kidney cells (COS-7) stably expressing one of the five recently cloned SSTR subtypes, human somatostatin receptor subtype 4, using whole cell voltage clamp technique at room temperature (20-23$ sp circ$C). / The outward current produced by a sequence of depolarizing steps from a holding potential of $-$80 mV was enhanced by $>$1 nM SST-14. Both the endogenous and SST-14 enhanced outward current had a high threshold ($ sim -$40 mV). The reversal potentials of their tail currents changed with a change of (K$ sp+ rbrack sb{ rm o}$ as expected for a current carried predominantly by K$ sp+$ ions. It was blocked by TEA (10-20 mM) and Ba$ sp{2+}$ (1 mM), but not by charybdotoxin (100 nM) and carbachol (50 $ mu$M) in the extracellular solution suggesting that it is largely due to a delayed rectifier K$ sp+$ channel. / A smaller inward current at potentials negative to $ sim -$60 mV was also observed and was enhanced by SST-14 in a similar concentration range. It was blocked by Ba$ sp{2+}$ (1 mM) and Cs$ sp+$ (1 mM) suggesting that SST-14 also enhances an inward rectifier K$ sp+$ current. Both outward and inward currents enhanced by SST-14 were pertussis toxin and cAMP sensitive.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.24023 |
| Date | January 1996 |
| Creators | Lu, Jun, 1969- |
| Contributors | Glavinovic, M. (advisor) |
| 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 | Master of Science (Department of Physiology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001529658, proquestno: MM19832, Theses scanned by UMI/ProQuest. |
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