盐度胁迫对云纹石斑鱼鳃离子调节酶及渗透压的影响

Impact of the abrupt salinity decrease on ion-regulation enzyme activity in the gill and serum osmolality from Epinehelus moara

为探讨云纹石斑鱼鳃离子调节酶活力及血清渗透压对盐度骤降的响应,设置4个盐度梯度(27、21、15和9)对云纹石斑鱼进行盐度骤降胁迫试验,在0、1 d、2 d、3 d和7 d时取样,测定其鳃中Na+/K+-ATP(NKA)酶、Ca^(2+)-ATP酶(Ca^(2+)-ATPase)、琥珀酸脱氢酶(SDH)、乳酸脱氢酶(LDH)活力及血清渗透压。结果表明,盐度21组与15组NKA及Ca^(2+)-ATPase活力在第1 d大幅上升,显著高于对照组(p<0.05),随后下降趋于稳定,而盐度9组NKA及Ga2+-ATPase活力一直呈下降趋势;血清渗透压呈先下降后上升的变化趋势(p<0.05);SDH活力变化与离子酶一致(p<0.05);LDH活力变化与离子酶相反(p<0.05)。研究表明,在盐度骤降的情况下,云纹石斑鱼鳃进行渗透压调节分为两个阶段,一是应激反应阶段,此时NKA及Ca^(2+)-ATPase迅速升高,血清渗透压降低;二是适应阶段,离子酶活力下降趋于稳定,血清渗透压升高恢复至正常水平,而且SDH与LDH酶活力也相应变化,为渗透压调节提供能量。

This paper is inclined to make an investigation and exploration of the response of the ion-regulatory enzyme activities in the gill and serum osmolality of Epinehelus moara in case of the abrupt salinity decrease. For the said research purpose,we have tested the four salinity levels（ 27,21,15,9） and done experiments by using a circular glass cylinder barrel of 1 m in diameter and 0. 8 m in depth. Taking natural seawater salinity of 27 as the control group,we have obtained the groups for treatment（ salinities of 21,15,9） by mixing the purified tap water with the natural seawater through 48 h aeration,and each group has been conducted in 3 buckets as three parallels,with gills being sampled for a period of time of 0,1 d,2 d,3 d,till 7 d to test the activities of Na^＋/K^＋-ATPase（ NKA）,Ca^2＋-ATPase,succinate dehydrogenase（ SDH）,lactate dehydrogenase（ LDH） and the serum osmolality. The experiment results we have gained show that NKA and Ca^2＋-ATPase activities have been found increasing significantly for the first day（ p〈 0. 05）,but tend to decrease on the second day in salinity 21 and 15. Nevertheless,the activities of the two kinds of enzyme in salinity 9 may tend to decrease,so does the serum osmolality（ p〈 0. 05）. And,SDH activity tends to be consistent with the variation of NKA and Ca^2＋-ATPase activities,though LDH activity tends to go contrarily（ p 0. 05）.Thus,it can be seen that the abrupt decrease of the salinity can significantly influence the ion-regulatory enzyme activities and serum osmolality of E. moara. What is more,the acclimatization can be supposed to be divided into two steps： the first step is the quick reaction period,whereas the serum osmolality tends to decline quickly and even trigger a change in the organic osmoregulation so as to promote the activities of NKA and Ca^2＋-ATPase.And,the second step can be regarded as a recovery phase,in which the serum osmolality tends to get reverted to the level back before the salinity changing,with ATPase dipped to the lowest level,and,then,getting to be returned slowly to the original leve1. And,so do SOD and LDH activities for the corresponding change,providing necessary energy for the said osmoregulation process.