Sodium or potassium ions activate different kinetics of gill Na, K-ATPase in three seawater- and freshwater-acclimated euryhaline teleosts
✍ Scribed by Lin, Chia-Hao ;Lee, Tsung-Han
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 150 KB
- Volume
- 303A
- Category
- Article
- ISSN
- 1548-8969
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✦ Synopsis
The effects of [Na + ] or [K + ] on Na, K-ATPase activity of FW-acclimated and SWacclimated tilapia, puffer and milkfish were examined in gill homogenates. [Na + ] or [K + ] stimulated Na, K-ATPase hydrolyzing ATP in all experimental groups. ATP hydrolysis stimulated by [Na + ] or [K + ] followed Michaelian-Menten kinetics. Km values for [K + ] (i.e., Km K ), were lower in SW-than FW-acclimated tilapia and puffer fishes (tilapia: 8.6970.22 vs. 11.9371.17 mM; puffer: 13.5171.39 vs. 30.5272.66 mM). Km values for [Na + ] (i.e., Km Na ), were lower in FW-than SW-acclimated milkfish (3.7670.54 vs. 7.5571.08 mM). These data suggest that [K + ] stimulates ATP hydrolysis to rates higher in SW-than FW-acclimated tilapia and puffer fishes, while [Na + ] stimulated ATP hydrolysis at rates higher in FW-than SW-acclimated milkfish. This is the first demonstration that Na, K-ATPase activity of euryhaline tilapia, puffer, and milkfish modulated by [Na + ] or [K + ] have different effects between FW-and SW-acclimated groups. Such responses as changes in properties of branchial Na, K-ATPase may contribute to improve the osmoregulatory capacity of tilapia, puffer and milkfish to acclimate in seawater and fresh water.