Combined effect of temperature and salinity on the Na+-K+-ATPase activity from the gill of GIFT tilapia juveniles(Oreochromis niloticus)
温度和盐度对吉富品系尼罗罗非鱼幼鱼鳃Na+-K+-ATPase活力的联合效应

Central composite face-centered design(CCF) and response surface methodology were used in the experiment to examine the combined effect of temperature(12—34℃) and salinity(0—26) on the Na+-K+-ATPase activity from the gill of tilapia juveniles(GIFT strain)(mean body length(4.3±0.105)cm and mean body weight(2.45±0.153)g).The results showed that:(1)The linear and quadratic effects of temperature and salinity on the Na+-K+-ATPase activity were highly significant(P<0.01),and the interactive effect between temperature and salinity was nonsignificant(P>0.05);(2)Using the response surface method,the Na+-K+-ATPase activity varied with increasing temperature and salinity in a curvilinear way;(3)The model equation of the enzyme activity towards temperature and salinity was established,with R2=0.9829 and Pred.R2=0.855(P<0.01).The model equation could be practically used for forecasting the gill Na+-K+-ATPase activity in GIFT Nile tilapia juveniles;(4)Via applying statistical optimization of the response of interest,results showed that the optimal factor combination was 24.15℃/11.75,at which the minimum Na+-K+-ATPase activity,0.62μmolPi·mg-1pr·h-1,was reached,with the desirability as high as 0.961.The Na+-K+-ATPase activity can be used as an indicator of growth of GIFT Nile tilapia juveniles.In general,It can be said that the environment in which the Na+-K+-ATPase activity is weaker is suitable for the tilapia juvenile growth,and in this case the metabolism of tilapia is more efficient,and the energy consumed for osmoregulation is smaller.