Cellular and molecular mechanisms of energy metabolism in fish gill during acclimation to salinity
Date Issued
2006
Date
2006
Author(s)
Lee, Jay-Ron
DOI
zh-TW
Abstract
Upon a salinity challenge, euryhaline teleosts immediately regulate the functions of many ion transporters and enzymes in the gill mitochondria-rich (MR) cells for maintaining their internal homeostasis. Large amount of energy is necessary for the operations of these transporters and enzymes, however the mechanism of energy metabolism in fish gills is still unclear. On the other hand, in mammalian central nervous system lactates, instead of glucose, are the main energy substrate transported from astrocyte to neuron via monocarboxylate transporter (MCT). Lactate dehydrogenase 1 (LDH1) is the key enzyme to convert the lactate to pyruvate, and LDH5 is responsible for the reverse reaction.
In the present study, we used tilapia (Oreochromis mossambicus) as a model animal to investigate the roles of LDHs in the energy metabolism of fish gills during acclimation to seawater (SW). Results of starch gel electrophoresis and western blot demonstrated that LDH1 is the major form and LDH5 the minor form expressed in tilapia gill epithelial cells. Immunocytochemical experiments indicated that both LDH1 and LDH5 were expressed in MR cells (Na+-K+ ATPase as a marker) and glycogen-rich cells. The protein expression level of LDH1 and citrate synthase increased immediately at the 1st h after acclimation to SW, while that of LDH 5 significantly enhanced during the 1st-3rd h. Taking all together, we proposed a energy metabolism model in gill epithelial cells during SW acclimation: The tricarboxylic acid cycle (TCA cycle) in MR cells is stimulated to produce enormous amount of energy for maintaining homeostasis and ion regulation at the 1st h after transfer to SW. Subsequently at the 3rd h, the LDH5 in MR cells is stimulated to enhance anaerobic respiration to produce emergent energy.
Subjects
能量代謝
乳酸脫氫酶
鰓
lactate dehydrogenase
energy metabolism
gill
Type
other
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