Calcium uptake mechanism in zebrafish embryos
| Autor: | Tien-chien Pan, 潘天健 |
|---|---|
| Rok vydání: | 2003 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 91 Vertebrates use Ca2+ as the major element for the formation of skeleton, which provides support and movement ability for individuals. In fish, water serves as a main source of Ca2+ than food, and gill has been proved to be the major Ca2+ uptake site that is responsible for more than 80% Ca2+ absorption. Ca2+ uptake occurs actively and also transcellularly through mitochondria-rich (MR) cells. The activities of plasma membrane Ca2+-ATPase (PMCA) and Na+-Ca2+ exchanger (NCX) have been identified in basolateral membrane of MR cells. PMCA and NCX have also been shown to be responsible for extruding Ca2+ into plasma. In the apical membrane, a Ca2+ channel is presumed to mediate Ca2+ entry, but there are no substantial molecular or physiological evidences for such channel in fish. The purpose of the present study is to identify the Ca2+ channel and elucidate its role in Ca2+ absorption. Zebrafish has been used extensively for the research of gene expression and developmental biology was selected as the model animal. In the present study, zebrafish ECaC (zECaC) from gill was cloned, sequenced, and the tissue distribution, developmental expression, and cellular localization of the zECaC were also studied. In addition, Ca2+ influx, Ca2+ content, and MR cell differentiation in different developmental stages of embryos were examined. The cloned zECaC is 2578 bp in legnth and encodes a protein of 709 amino acids. According to the phylogenetic analysis, trout and zebrafish ECaC were clustered together and formed a distinct group from amphibian and mammalian ones. It indicates that the duplication of ECaC may occur after the divergence of fish and mammals. zECaC was found to express ubiquitously in all the tissues examined, and started to express in embryos at 24 hours post fertilization (hpf). Ca2+ influx started to increase at 36 hpf while Ca2+ content accumulated after hatching. MR cells appeared on the embryos at 24 hpf, but first opening was observed at 36 hpf. According to the results, the timing of MR cell differentiation corresponded with the data of Ca2+ influx, and it implies a definite need for Ca2+ uptake from ambient environment during larval development. The zECaC expression pattern during development correlated with the first appearance of MR cell and also Ca2+ influx. Moreover, zECaC expression in gill was localized along the gill filaments where MR cells were concentrated. In conclusion, zECaC is first cloned in the present study, and it is expressed in all the tissues examined, including MR cells in gill. The wide tissue distributions suggest that zECaC may play a key role in Ca2+ absorption in developing embryo and also in adult fish. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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