Please use this identifier to cite or link to this item: http://hdl.handle.net/10497/17115
Title: Light induces changes in activities of Na+/K+-ATPase, H+/K+-ATPase and glutamine synthetase in tissues involved directly or indirectly in light-enhanced calcification in the giant clam, Tridacna squamosa
Authors: Ip, Yuen Kwong
Ching, Biyun
Hiong, Kum Chew
Choo, Celine Yen Ling
Boo, Mel Veen
Wong, Wai Peng
Chew, Shit Fun
Keywords: Ammonia
Ca2+-ATPase
H+-ATPase
Mantle
Tridacnid
Zooxanthellae
Issue Date: 2015
Citation: Ip, Y. K., Ching, B., Hiong, K. C., Choo, C. Y. L., Boo, M. V., Wong, W. P., & Chew, S. F. (2015). Light induces changes in activities of Na+/K+-ATPase, H+/K+-ATPase and glutamine synthetase in tissues involved directly or indirectly in light-enhanced calcification in the giant clam, Tridacna squamosa. Frontiers in Physiology, 6: 68. doi: 10.3389/fphys.2015.00068
Abstract: The objective of this study was to determine the effects of 12h of exposure to light, as compared with 12h of exposure to darkness (control) on enzymatic activities of transporters involved in the transport of NH+4 or H+, and activities of enzymes involved in converting NH+4 to glutamate/glutamine in inner mantle, outer mantle, and ctenidia of the giant clam, Tridacna squamosal. Exposure to light resulted in a significant increase in the effectiveness of NH+4 in substitution for K+ to activate NA+/K+-ATPase(NKA), manifested as a significant increase in the NA+/NH+4-activated-NKA activity in the inner mantle. However, similar phenomena were not observed in the extensible outer mantle, which contained abundant symbiotic zooxanthellae. Hence, during light-enhanced calcification, H+ released from CaCO3 deposition could react with NH3 to form NH+4 in the extrapallial fluid, and NH+4 could probably be transported into the shell-facing inner mantle epithelium through NKA. Light also induced an increase in the activity of glutamine synthetase , which converts NH+4 and glutamate to glutamine, in the inner mantle. Taken together, these results explained observations reported elsewhere that light induced a significant increase in pH and a significant decrease in ammonia concentration in the extrapallial fluid, as well as a significant increase in the glutamine concentration in the inner mantle, of T. squamosa. Exposure of T. squamosa to light also led to a significant decrease in the N-ethylmaleimide (NEM)-sensitive-V-H+-ATPase (VATPase) in the inner mantle, and significant increases in the NA+/K+-activated-NKA, H+/NH+4-activated-H+/K+-ATPase, and NEM-sensitive-VATPase activities in ctenidia, indicating that light-enhanced calcification might perturb Na+ homeostasis and acid/base balance in the hemolymph , and might involve the active uptake of NH+4 from the environment. This is the first report on light having direct enhancing effects on activities of certain transporters/enzymes related to light-enhanced calcification in the inner mantle and ctenidia of T. squamosa.
URI: http://hdl.handle.net/10497/17115
ISSN: 1664-042X (online)
Other Identifiers: 10.3389/fphys.2015.00068
Website: http://dx.doi.org/10.3389%2Ffphys.2015.00068
Appears in Collections:Journal Articles

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