title: Inhibition of calcium uptake during hypoxia in developing zebrafish is mediated by hypoxia-inducible factor.
abstract: The present study investigated the potential role of hypoxia-inducible factor (HIF) in calcium homeostasis in developing zebrafish (Danio rerio). It was demonstrated that zebrafish raised in hypoxic water (30 mmHg; control, 155 mmHg PO2) until 4 days post-fertilization exhibited a substantial reduction in whole-body Ca2+levels and Ca2+uptake. Ca2+uptake in hypoxia-treated fish did not return to pre-hypoxia (control) levels within 2 h of transfer back to normoxic water. Results from real-time PCR showed that hypoxia decreased the whole-body mRNA expression levels of the epithelial Ca2+channel (ecac), but not plasma membrane Ca2+-ATPase (pmca2) or Na+/Ca2+-exchanger (ncx1b). Whole-mount in situ hybridization revealed that the number of ecac-expressing ionocytes was reduced in fish raised in hypoxic water. These findings suggested that hypoxic treatment suppressed the expression of ecac, thereby reducing Ca2+influx. To further evaluate the potential mechanisms for the effects of hypoxia on Ca2+regulation, a functional gene knockdown approach was employed to prevent the expression of HIF-1αb during hypoxic treatment. Consistent with a role for HIF-1αb in regulating Ca2+balance during hypoxia, the results demonstrated that the reduction of Ca2+uptake associated with hypoxic exposure was not observed in fish experiencing HIF-1αb knockdown. Additionally, the effects of hypoxia on reducing the number of ecac-expressing ionocytes was less pronounced in HIF-1αb-deficient fish. Overall, the current study revealed that hypoxic exposure inhibited Ca2+uptake in developing zebrafish, probably owing to HIF-1αb-mediated suppression of ecac expression.
authors: Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 6N5 rwmkwong@yorku.ca.|Department of Biology, York University, Toronto, ON, Canada, M3J 1P3.
authors: Raymond W M
authors: 0000-0002-0784-9651
authors: RW
authors: Kwong
authors: Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 6N5.
authors: Yusuke
authors: Y
authors: Kumai
authors: Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 6N5.
authors: Velislava
authors: V
authors: Tzaneva
authors: Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 6N5.
authors: Estelle
authors: E
authors: Azzi
authors: Institute of Zoology, University of Innsbruck, Innsbruck A-6020, Austria.
authors: Nina
authors: N
authors: Hochhold
authors: Department of Integrative Biology, University of Guelph, Guelph, ON, Canada, N1G 2W1.
authors: Cayleih
authors: C
authors: Robertson
authors: Institute of Zoology, University of Innsbruck, Innsbruck A-6020, Austria.
authors: Bernd
authors: B
authors: Pelster
authors: Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 6N5.
authors: Steve F
authors: SF
authors: Perry
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000235:genetics; D002118:Calcium / Q000378:metabolism*; D002452:Cell Count; D005786:Gene Expression Regulation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D000860:Hypoxia / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D007477:Ions; D060172:Morpholinos / Q000494:pharmacology; D055550:Protein Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism; D015027:Zebrafish / Q000235:genetics / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007477:Ions; D060172:Morpholinos; D012333:RNA, Messenger; D050916:TRPV Cation Channels; D029961:Zebrafish Proteins; C000621936:hif1aa protein, zebrafish; C505134:trpv6 protein, zebrafish; D002118:Calcium
keywords: Calcium; ECaC; Fish; HIF; Ion regulation; Ionocyte