Cellular distributions of creatine kinase in branchia of euryhaline tilapia (Oreochromis mossambicus)

Abstract

Although euryhaline teleosts can adapt to environmental fluctuation of salinity, their energy source for responding to changes in salinity and osmolarity remains unclear. This study examines the cellular localization of creatine kinase (CK) expression in branchia of tilapia (Oreochromis mossambicus). Western blot analysis of muscle-type CK (MM form) revealed a high association with salinity changes, but BB and MB forms of CK in the gills of fish adapted to seawater did not change. With the use of immunocytochemistry, three CK isoforms (MM, MB, and BB) were localized in mitochondria-rich (MR) cells and other epithelial cells of tilapia gills. In addition, staining intensity of MM-form CK in MR cells increased after seawater transfer, whereas BB and MB forms did not significantly change. To our knowledge, this work presents the first evidence of CK expression in MR cells of tilapia gills, highlighting the potential role of CK in providing energy for ion transport. creatine kinase isoform; mitochondria-rich cells; gill CREATINE KINASE (CK; EC 2.7.3.2) catalyzes the reversible transfer of the phosphoryl group from phosphocreatine to ADP, regenerating ATP. CK participates in an ubiquitous role to meet the energy demand for homeostasis during environmental changes. The phosphocreatine/creatine kinase is present in some excitable tissues, such as Narcine brasiliensis electric organ (2), and in nonexcitable tissues, such as Squalus acanthias rectal gland (10), Gillichthys mirabilis gills (15), and Oreochromis mossambicus gills (37), with high and fluctuating energy demand. Plasma CK exhibits the physiological stress responses in big game fish after capture, perhaps because of muscle damage and subsequent release of cytosolic soluble CK in the plasma (36). Total CK activity significantly declined 20% in the fish (O. mossambicus) brain after exposure to hypergravity for 7 days (30). Additionally, some evidence has demonstrated seasonal fluctuations of CK in rainbow trout, Oncorhynchus mykiss (3), variability of CK isoenzymes in various tissues of trout (22), and genetic variability in tissue CK among fish species including rainbow trout and salmon (22,26). Furthermore, CK provides energy for ion transport (Na ϩ -K ϩ -ATPase) in the gill of G. mirabilis when the CK inhibitor iodoacetamide is used (15). It seems that the phosphocreatine/creatine kinase shuttle in cytosol might coordinate with that in mitochondria to provide more ATP for the extra energy demand of Na ϩ -K ϩ -ATPase to pump out excess ions under hypertonic conditions. The results imply that CK may be a good candidate for converting the energy after seawater transfer.Many CK isoforms are identified by their electrophoretic mobility, tissue and subcellular distribution, and primary sequence (24, 34). Three cytosolic CK isozymes [BB-CK (brain), MM-CK (muscle), and MB-CK (heart, lungs, stomach) (5, 8)] and two mitochondrial forms [sarcomeric MiCK (expressed mainly in heart and skeletal muscle and probably in some brain cells such as Purkinje neurons) and ubiquito...

Effects of dietary creatine on juvenile hybrid striped bass in low‐salinity and brackish waters

“…Osmoregulation is primarily in the gills and intestine of fish (Gatlin III et al, 1992; Jackson, McCormick, Madsen, Swanson, & Sullivan, 2005). The creatine‐creatine phosphate shuttle, where creatine acts as a regenerative source of phosphate for ATP, has been recognized in the gills of fish (Kultz & Somero, 1995; Lin et al, 2003). Thus, increased circulating creatine could be taken up by gills, and energetically assist in osmoregulation.…”

“…A creatine‐creatine phosphate shuttle has been recognized in fish gills (Kultz & Somero, 1995; Lin et al, 2003), and much like NKA, creatine kinase activity increases during times of osmotic stress (Weng et al, 2002). Therefore, there is potential for dietary creatine to support ion exchange for osmoregulation.…”

Ontogeny of the Osmoregulatory Capacity of Teleosts and the Role of Ionocytes

“…Subsequent work established that fish gill epithelia expressed large quantities of Na + /K + -ATPase (NKA) whose activity was usually proportional to the external salinity (De Rengis and Bornancin, 1984;McCormick, 1995). This has been attributed to an increased α-subunit mRNA abundance (Madsen et al, 1995;Singer et al, 2002) and protein amount (Lee et al, 2000;Tipsmark et al, 2002;Lin et al, 2003) or both (D'Cotta et al, 2000;Lin and Hwang, 2004).…”

Creatine: A valuable supplement in aquafeeds?

“…Remarkably, effective dose of creatine (4% of dry food, 5%–7% feeding ratio, corresponding approximately to 2–2.8 g kg −1 body weight) was very high compared to the dosage used for application in humans. The phosphocreatine/creatine kinase shuttle seems to coordinate the extra energy demand of the Na + ‐K + ‐ATPase to pump out excess ions under hyperosmotic conditions 109 . During times of osmotic stress, creatine kinase activity increases, suggesting that creatine supplementation has ergogenic benefits 109–111 .…”