Neuroepithelial cells (NECs) of the zebrafish gill filament have been previously identified as bimodal O2 and CO2/H+ sensors that depolarize in response to chemostimuli via inhibition of background K+ channels. To further elucidate the signaling pathway underlying CO2/H+ chemoreception in the NECs we employed microspectrofluorometric techniques to examine the effects of hypercapnia on [Ca2+]i and pHi. NECs increased their [Ca2+]i in response to acidic hypercapnia (5% CO2, pH 6.6) and isocapnic acidosis (normocapnia, pH 6.6), but not to isohydric hypercapnia (5% CO2, pH 7.8). The acid- induced increase in [Ca2+]i persisted in the absence of extracellular Ca2+, and Ca2+ channel blockers (Cd2+, Ni2+ and nifedipine). NECs exhibited a rapid and reversible drop in pHi in response to acidic hypercapnia and isohydric hypercapnia. Isocapnic acidosis also induced intracellular acidification within NECs, but it was less severe than the drop in pHi elicited by acidic hypercapnia and isohydric hypercapnia. The rate and magnitude of intracellular acidification was reduced by the CA-inhibitor, acetazolamide, without effect on the acid-induced increase in [Ca2+]i. Acetate was used to investigate the relationship between pHi and [Ca2+]i. Acetate induced intracellular acidification without augmentation of [Ca2+]i. The results of this thesis demonstrate that (1) extracellular acidification, but not CO2, is critical to the hypercapnia-induced increase in [Ca2+]i (2) the increase in [Ca2+]i is independent of the drop in pHi (3) the increase in [Ca2+]i is not mediated by the influx of Ca2+ across the plasma membrane.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OOU-OLD./23775 |
| Date | 04 February 2013 |
| Creators | Abdallah, Sara |
| 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 | Thèse / Thesis |
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