Lipid composition and microsomal ATPase activities in gills and kidneys of warm- and cold-acclimated sea bass (Dicentrarchus labrax L.)

Abstract

The response to cold of gill and kidney membrane lipid composition and microsomal (Na(+)+K(+))-ATPase, Na(+)-ATPase and Mg(2+)-ATPase activities in reared sea bass (Dicentrarchus labrax L.) was investigated. Fish acclimation was carried out according to the seasonal cycle from August to March. No cold-promoted increase in fatty acid unsaturation was shown in gill and kidney polar lipids and in total lipids of mitochondria and microsomes. In both tissues the (Na(+)+K(+))-ATPase exhibited positive compensation for cold acclimation whereas the Na(+)-ATPase displayed negative compensation. The Mg(2+)-ATPase showed no compensation in the gills and positive compensation in the kidneys. During cold acclimation the break in the Arrhenius plot of the (Na(+)+K(+))-ATPase decreased, whereas breaks of both the Na(+)-ATPase and the Mg(2+)-ATPase activities remained unchanged. The results indicate that the sea bass does not adopt membrane unsaturation as a cold-facing strategy. The cold-promoted enhancement of (Na(+)+K(+))-ATPase activity in osmoregulatory tissues may be advantageous to maintain efficient osmoregulation under thermodynamically unfavourable conditions.

Muscle fatty acid composition and oxidative stress indices of Arctic charr, Salvelinus alpinus (L.), in relation to dietary polyunsaturated fatty acid levels and temperature

“…Overall, however, changes were small for fish maintained on the 500 g kg -1 PUFA diets, and seem to agree with other observations that changes in unsaturation may not be the main strategy to cold adaptation in fish (Skuladottir et al 1990;Ventrella et al 1993;Staurnes et al 1994). Nevertheless, unsaturation did increase following cold exposure in muscle PL of fish fed the 250 g kg -1 marine PUFA, and this finding agrees with liver data on Arctic charr (Olsen & Lie, unpublished data).…”

Membrane Lipid Microenvironment Modulates Thermodynamic Properties of the Na+-K+-ATPase in Branchial and Intestinal Epithelia in Euryhaline Fish In vivo

“…Slight differences in these parameters were detected for control enterocytes, but values for control gill epithelia were substantially different, being Td and Ea 1 higher than in enterocytes. Similar results have been observed in mucosal scrapings (Almansa et al, 2003) and branchial microsomal fractions from gilthead seabream (Ventrella et al, 1990) and in the sea bass Dicentrarchus labrax (Ventrella et al, 1993) reared under similar conditions.…”

“…Na + -K + -ATPase activities were measured in triplicate as the difference in inorganic phosphate (Pi) production from ATP in the presence or absence of 1 mM ouabain, under steady-state conditions, as described previously (Ventrella et al, 1990, 1993; Díaz et al, 1998; Almansa et al, 2001). Briefly, 25 μl of protein suspension, containing 50–100 μg protein, were added to test tubes containing 1 ml of incubation media (25 mM HEPES, 200 mM NaCl, 10 mM KCl, 5 mM MgCl2, and adjusted to pH 7.4 with TRIS) and allowed to preincubate for 5 min in a temperature-controlled water-jacketed chamber set at the desired temperature.…”

“…Later on, we found that differences in thermodynamic properties existed between intestinal segments from gilthead seabream and that these differences were likely due to different phospholipid microenvironment rather than to differential expression of α-subunits (Almansa et al, 2003). The influence of the lipid microenvironment composition on the thermodynamic and kinetic properties of the Na + -K + -ATPase is pervasive and has been recognized for long (Wheeler and Whittam, 1970; Klingenberg, 1975; Brasitus, 1983; Cornelius and Skou, 1984; Yeagle et al, 1988; Muriana et al, 1992; Gerbi et al, 1993, 1994; Ventrella et al, 1993). From these early studies it soon became clear that the degree of unsaturation of membrane phospholipids, as well as membrane cholesterol contents, played modulatory roles on the kinetic features of the Na + -K + -ATPase, which were initially interpreted as secondary to differences in membrane fluidity.…”

Response to T3treatment and changing environmental salinity of liver lipid composition, mitochondrial respiration and (Na++ ++ K++)-ATPase activity in rainbow troutOncorhynchus mykissWalbaum

“…The (Na + + K + )‐ATPase activity was evaluated for liver microsomes as the difference between the P i released in the reaction medium containing MgCl 2 , NaCl and KCl (total ATPase activity) and that liberated in the same reaction mixture in the absence of KCl or in the presence of 1 m m ouabain. The ATPase assays were carried out as reported previously (Ventrella, Pagliarani, Pirini, Trigari, Trombetti & Borgatti 1993). The reaction mixture, slightly modified from that adopted by Omeljaniuk & Eales (1986), contained 75 m m Hepes, 27 m m Tris, pH 7.2, 100 m m NaCl, 20 m m KCl and 5 m m MgATP.…”