In euryhaline fishes, atrial and B-type natriuretic peptides are important hormones in hypo-osmoregulation, whereas osmoregulatory functions of C-type natriuretic peptides (CNPs) remain to be investigated. Although four CNP isoforms (CNP1-4) are mainly expressed in the brain, multiorgan expression of CNP3 was found in euryhaline Japanese eel, Anguilla japonica. Here we identified the CNP3-expressing cells and examined their response to osmotic stress in eel. CNP3 was expressed in several endocrine cells: prolactin-producing cells (pituitary), glucagon-producing cells (pancreas), and cardiomyocytes (heart). Pituitary CNP3 expression was the highest among organs and was decreased following seawater transfer, followed by a decrease in the freshwater-adaptating (hyper-osmoregulatory) hormone prolactin. We also showed the negative correlation between CNP3/prolactin expression in the pituitary and plasma Cl⁻ concentration, but not for plasma Na⁺ concentration. These results suggest that CNP3 in the pituitary (and pancreas) plays a critical role in freshwater adaptation of euryhaline eel together with prolactin.

在鱼腥鱼中，心房和B型利尿钠肽是低渗调节中的重要激素，而C型利尿钠肽（CNP）的渗透调节功能仍有待研究。虽然4个CNP亚型（CNP1-4）主要表达在脑，CNP3的多器官中表达广盐日本鳗鲡发现，鳗鲡。在这里，我们鉴定了CNP3表达细胞，并检查了它们对鳗鱼渗透压的反应。CNP3在几种内分泌细胞中表达：催乳素产生细胞（垂体），胰高血糖素产生细胞（胰腺）和心肌细胞（心脏）。垂体CNP3表达在各器官中最高，并在海水转移后降低，其后淡水适应（高渗透调节）激素催乳素减少。我们还发现在垂体和血浆氯CNP3 /催乳素表达的负相关^-浓度，但不用于血浆的Na ⁺浓度。这些结果表明，垂体（和胰腺）中的CNP3在淡水鳗鱼鳗鱼和催乳素的适应中起着关键作用。