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First published online September 14, 2007
Journal of Experimental Biology 210, 3494-3504 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.007146

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Regulation of glycogen metabolism in gills and liver of the euryhaline tilapia (Oreochromis mossambicus) during acclimation to seawater

Joshua Chia-Hsi Chang¹, Su-Mei Wu², Yung-Che Tseng³, Yi-Chun Lee², Otto Baba⁴ and Pung-Pung Hwang^1,*

¹ Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan, Republic of China
² Department of Aquatic Biosciences, National Chiayi University, Chiayi, Taiwan, Republic of China
³ Institute of Zoology, National Taiwan University, Taipei, Taiwan, Republic of China
⁴ Department of Hard Tissue Engineering, Tokyo Medical and Dental University, Tokyo, Japan

View larger version (85K): [in this window] [in a new window]   Fig. 1. Full-length glycogen synthase cDNA and the deduced amino acid sequences cloned from tilapia gills. Five important phosphorylation sites (circles) and two UDP-glucose binding-related Lys residues (shaded) are all conserved. GenBank Accession No. EF565371.

View larger version (5K): [in this window] [in a new window]   Fig. 2. Phylogenic analysis constructed with complete amino acid sequences of glycogen synthase (GS) by maximum parsimony methods with 1000 replications. The GenBank Accession Nos of the sequences used are as follows: GS muscle form of the mouse, NP_109603; human, NP_002094; rat, XP_341859; rabbit, P13834; monkey, AF529178; zebrafish, NP_957474. GS liver form of the mouse, NP_663547; rat, NP_037221; human, NP_068776; zebrafish, NP_001018199. GS isoform C from Drosophila, NP_731968.

View larger version (27K): [in this window] [in a new window]   Fig. 3. RT-PCR analysis of glycogen synthase (GS) gene expression in the brain (B), gills (G), liver (L), muscle (M), intestines (I), heart (H), spleen (S) and kidneys (K) of tilapia. ß-Actin was used as an internal control. GS was expressed in all of the tissues examined, with the brain, muscle, heart and spleen showing higher expression levels.

View larger version (13K): [in this window] [in a new window]   Fig. 4. Western blot analysis of glycogen synthase in mouse muscle (MM), mouse kidney (MK), tilapia liver (TL) and isolated tilapia gill cells (TG). The anti-human glycogen synthase polyclonal antibody revealed immunoreactive bands with similar sizes in all the tissues.

View larger version (57K): [in this window] [in a new window]   Fig. 5. Immunohistochemical images of freshwater tilapia gill frozen sections. (A–C) Double labeling for glycogen synthase (GS) and Na+/K+-ATPase (NaK); (D–G) double labeling (arrows) for GS and glycogen phosphorylase (GP); (H–K) double labeling (arrows) for GS and glycogen. A, D and H are DIC images. GS, GP and glycogen were co-localized in a specific group of glycogen-rich cells (GRC) that are adjacent to mitochondrion-rich cells (MRC; labeled with Na+/K+-ATPase). White dots indicate the outline of the cells. Scale bar: 10 µm (A–C) and 20 µm (D–K).

View larger version (7K): [in this window] [in a new window]   Fig. 6. Time-course changes in gill Na+/K+-ATPase activities in tilapia transferred from freshwater (FW) to 25 seawater (SW). Data are presented as means ± s.d. (N=6). *Indicates a significant difference from the respective control in FW (P<0.05). Different letters indicate significant differences (P<0.05) among sampling times in fish transferred to SW.

View larger version (10K): [in this window] [in a new window]   Fig. 7. Time-course changes in gill (A) and liver (B) glycogen content in tilapia transferred from freshwater (FW) to 25 seawater (SW). Data are presented as means ± s.d. (N=6). *Indicates a significant difference from the respective control in FW (P<0.05). Different letters indicate significant differences (P<0.05) among sampling times in fish transferred to SW.

View larger version (14K): [in this window] [in a new window]   Fig. 8. Time-course changes of gill glycogen phosphorylase (GP) total activity (A), GP protein relative amounts (B) and glycogen synthase (GS) protein relative amounts (C) in tilapia transferred from freshwater (FW) to 25 seawater (SW). Protein amounts were measured by western blotting. Data are presented as means ± s.d. (N=6). *Indicates a significant difference from the respective control in FW (P<0.05). Different letters indicate significant differences (P<0.05) among sampling times in fish transferred to SW.

View larger version (11K): [in this window] [in a new window]   Fig. 9. Time-course changes in liver glycogen phosphorylase (GP) protein relative amounts (A) and glycogen synthase (GS) protein relative amounts (B) in tilapia transferred from freshwater (FW) to 25 seawater (SW). Protein amounts were measured by western blotting. Data are presented as means ± s.d. (N=6). *Indicates a significant difference from the respective control in FW (P<0.05). Different letters indicate significant differences (P<0.05) among sampling times in fish transferred to SW.