Effect of Dopamine Injection on the Hemocyte Count and Prophenoloxidase System of the White Shrimp Litopenaeus vannamei

Effects of dopamine injection on the hemocyte count, phenoloxidase activity, serine proteinase activity, proteinase in-hibitor activity and α2-macroglobulin-like activity in L. vannamei were studied. Results showed that dopamine injection resulted in a significant effect on the parameters measured (P < 0.05), while no significant difference was observed in the control group (0.85% NaCl). In the experimental groups,the hemocyte count reached the minimum in 3 h;granular and semi-granular cells became stable after 12 h and hyaline cells and the total hemocyte count became stable after 18 h. Phenoloxidase activity reached the minimum in 6 h, and then became stable after 9 h. Serine protease activity and proteinase inhibitor activity reached the minimum in 3 h, and α2-macro-globulin-like activity reached the maximum in 3 h,and all the three parameters became stable after 12 h. The results suggest that the activating mechanisms of the proPO system triggered by dopamine are different from those triggered by invasive agents or sponta-neously activated under a normal physical condition.

Responses of Prophenoloxidase System and Related Defence Parameters of Litopenaeus vannamei to Low Salinity

In this study,we investigated the effects of low salinity(26 and 21) on the prophenoloxidase(proPO) system and related defence parameters in the shrimp Litopenaeus vannamei.The results showed that low salinity induced a significant increase of dopamine(DA) concentration in haemolymph at 6 h of the experiment;on the other hand,total haemocyte count(THC),differential haemocyte count(DHC) and PO activity decreased over time to the lowest level at 24 h and remained low thereafter.Serine Protease(SP) and Proteinase Inhibitor(PI) activity in the two lower salinity treatments decreased to the lowest level at 12 and 24 h,respectively,and both recovered to the control level at 72 h.In contrast,α2-macroglobulin(α2M) activity in the two lower salinity treatments peaked at 24 h and then decreased to the control level at 72 h.Therefore,it may be concluded that stress-induced DA plays an important temporary role in neurotransmission and causes immune response in L.vannamei in adapting to salinity changes.

Modulation by Biogenic Amines for the Hemocyte Count and Prophenoloxidase Exocytosis via Receptors in Litopenaeus vannamei

Hemocyte counts and phenoloxidase(PO)activity were examined after hemolymph being incubated in dopamine(DA),noradrenaline(NE)and serotonin(5-HT).Results showed that all the three biogenic amines(BAs)had a significant impact on total hemocyte count(THC),differential hemocyte count(DHC),and intracelluar and extracelluar phenoloxidase(PO)activity.Among these Bas,DA had the strongest effect on the above parameters,whereas 5-HT had the least effect.Preincubation with D1 receptor antagonist SCH23390,D2 receptor antagonist Sulpiride and 1:1 admixture of the two could significantly inhibit the effect of DA on these parameters.SCH23390 showed a stronger inhibitory effect than Sulpiride,and the admixture exhibited the strongest effect.These results suggested that the change of hemocyte count and activation of prophenoloxidase(proPO)system in Litopenaeusvan-namei hemocyte can be regulated by BAs,and DA modulates the two parameters via its receptors.

低溶解氧对凡纳滨对虾酚氧化酶原激活系统和相关免疫因子的影响

本文研究了凡纳滨对虾在低溶解氧条件下酚氧化酶原系统的激活机制。结果表明:低溶氧(1.5mg/L,3.0mg/L)胁迫对凡纳滨对虾血淋巴中多巴胺含量、血细胞数量、酚氧化酶原激活系统相关酶活力、血淋巴中类α2-巨球蛋白活力影响显著(P<0.05),且各指标表现出明显的时间效应性。在实验时间内,DO为3.0mg/L处理组,总血细胞、小颗粒细胞和透明细胞数量均在12h内降低而后趋于稳定,大颗粒细胞数量在24h内降低后保持稳定,DO为1.5mg/L处理组,总血细胞数量和三类血细胞数量均在24h内降低而后趋于稳定;DO为3.0mg/L和1.5mg/L处理组凡纳滨对虾血淋巴中多巴胺含量分别在24h、12h内呈峰值变化,至12h、6h时达到最大值,在24h、12h后恢复至对照组水平并趋于稳定;血细胞中酚氧化酶原活力分别在12h、6h时显著降低,且均在24h时趋于稳定;丝氨酸蛋白酶活力在6h时均显著降低,在24h时达到最低值,而后趋于稳定,蛋白酶抑制剂活力显著降低,但类α2-巨球蛋白活力48h内呈峰值变化,与对照组比较均显著升高,48h后趋于稳定。实验期内对照组DO为5.5mg/L各指标变化不显著。