Yada T, Kaiya H, Mutoh K, Azuma T, Hyodo S, Kangawa K
Freshwater Fisheries Research Department, National Research Institute of Fisheries Science, 2482-3 Chugushi, Nikko, Tochigi 321-1661, Japan.
J Endocrinol. 2006 Apr;189(1):57-65. doi: 10.1677/joe.1.06187.
To clarify the role of ghrelin in the fish immune system, the in vitro effect of ghrelin was examined in phagocytic leukocytes of rainbow trout (Oncorhynchus mykiss). Administration of trout ghrelin and des-VRQ-trout ghrelin, in which three amino acids are deleted from trout ghrelin, increased superoxide production in zymosan-stimulated phagocytic leukocytes from the head kidney. Gene expression of growth hormone (GH) secretagogue-receptor (GHS-R) was detected by RT-PCR in leukocytes. Pretreatment of phagocytic leukocytes with a GHS-R antagonist, [D-Lys3]-GHRP-6, abolished the stimulatory effects of trout ghrelin and des-VRQ-trout ghrelin on superoxide production. Ghrelin increased mRNA levels of superoxide dismutase and GH expressed in trout phagocytic leukocytes. Immunoneutralization of GH by addition of anti-salmon GH serum to the medium blocked the stimulatory effect of ghrelin on superoxide production. These results suggest that ghrelin stimulates phagocytosis in fish leukocytes through a GHS-R-dependent pathway, and also that the effect of ghrelin is mediated, at least in part, by GH secreted by leukocytes.
为阐明胃饥饿素在鱼类免疫系统中的作用，研究了胃饥饿素对虹鳟（Oncorhynchus mykiss）吞噬性白细胞的体外效应。给头肾来源的经酵母聚糖刺激的吞噬性白细胞注射虹鳟胃饥饿素和去-VRQ-虹鳟胃饥饿素（从虹鳟胃饥饿素中缺失三个氨基酸），可增加超氧化物的产生。通过RT-PCR在白细胞中检测生长激素（GH）促分泌素受体（GHS-R）的基因表达。用GHS-R拮抗剂[D-Lys3]-GHRP-6预处理吞噬性白细胞，可消除虹鳟胃饥饿素和去-VRQ-虹鳟胃饥饿素对超氧化物产生的刺激作用。胃饥饿素可增加虹鳟吞噬性白细胞中表达的超氧化物歧化酶和GH的mRNA水平。向培养基中添加抗鲑鱼GH血清对GH进行免疫中和，可阻断胃饥饿素对超氧化物产生的刺激作用。这些结果表明，胃饥饿素通过GHS-R依赖性途径刺激鱼类白细胞的吞噬作用，并且胃饥饿素的作用至少部分是由白细胞分泌的GH介导的。
