Exploring of the role of the ghrelin system in homeostatic regulation in amphibians

在这项研究中，我们在三种无尾两栖动物(牛蛙、日本树蛙和日本蟾蜍)和一种有尾目动物(日本火腹螈)中发现了Ghrelin受体(GHS-R1a)。功能分析表明，Anura的Ghrelin受体不识别Ghrelin的第三个氨基酸的丝氨酸或苏氨酸，而Newt的Ghrelin受体与丝氨酸有很高的亲和力。我们研究了Ghrelin对腹腔注射后的摄食调节的影响。同源的Ghrelin对蝾螈没有影响，但增加了牛蛙幼虫的摄食量。然而，禁食会影响Newt中Ghrelin和GHS-R1a基因的表达。总体而言，Ghrelin系统参与了两栖动物的能量平衡。我们的发现为Ghrelin在脊椎动物中的功能提供了新的证据。

In this study, we identified ghrelin receptors (GHS-R1a) in three species of Anura (bullfrog, Japanese tree frog, and Japanese toad) and one species of Caudata (Japanese fire-belly newt). Functional analyses revealed that ghrelin receptors for Anura did not recognize serine or threonine at the third amino acid of ghrelin, but that of newt showed a high affinity for ghrelin with serine. We examined the effect of ghrelin on feeding regulation after intraperitoneal injection. Homologous ghrelin had no effect in newt, but increased food intake in bullfrog larvae. However, a fasting affects expressions of ghrelin and GHS-R1a genes in newt. Overall, it is suggested that the ghrelin system participates in energy homeostasis in amphibians. Our findings provide new evidences to ghrelin function in vertebrates.