Abstract
IntroductionThe adrenomedullins (AMs) comprise a hormonal family in mammals and teleost fishes, with five members (AM1–5) found or predicted in most of the teleosts including Japanese medaka (Oryzias latipes). AM1 is known to have cardiovascular and osmoregulatory functions in mammals, but the roles of most AMs are yet to be determined.ResultsUsing medaka, we first analyzed the tissue distribution of all five AM genes and found detectable expression in all tissues examined, with relatively high levels of AM3 and AM5 in the liver and kidney. To assess the osmoregulatory roles of these AMs, mRNA levels were examined in the brain (including the eyes), gill, liver, kidney and spleen of medaka one week after transfer from isotonic saline (11 ppt) to freshwater (0 ppt) or seawater (33 ppt). Expression of AM1 in the brain-eye increased in freshwater. The central level of AM4 (the paralog of AM1) decreased in seawater; the branchial level of AM4 decreased in freshwater and seawater, but the renal level increased in freshwater. The branchial level of AM2 increased in seawater, whereas the renal level decreased in freshwater and seawater. Expression of AM3, the AM2 paralog, decreased in the brain-eye of seawater-acclimated fish. Expression of AM5 in the brain-eye and kidney decreased in seawater.ConclusionsExcept for branchial AM2, the members of AM family tend to be involved in promotion of hyper-osmoregulation and/or inhibition of hypo-osmoregulation, although each AM may play a distinct role during adaptation to different salinities.
Highlights
The adrenomedullins (AMs) comprise a hormonal family in mammals and teleost fishes, with five members (AM1–5) found or predicted in most of the teleosts including Japanese medaka (Oryzias latipes)
AM1 was initially thought to be a member of the calcitonin generelated peptide (CGRP) family, together with CGRP and amylin
The AM4 mRNA level was much higher in fish transferred to freshwater, compared to the levels in 11 ppt control and seawater (Figure 2B)
Summary
The adrenomedullins (AMs) comprise a hormonal family in mammals and teleost fishes, with five members (AM1–5) found or predicted in most of the teleosts including Japanese medaka (Oryzias latipes). AM1 is known to have cardiovascular and osmoregulatory functions in mammals, but the roles of most AMs are yet to be determined. Adrenomedullin (AM) is a peptide hormone that was first isolated from human pheochromocytoma in 1993 [1]. AM1 was initially thought to be a member of the calcitonin generelated peptide (CGRP) family, together with CGRP and amylin. Our group discovered five distinct AMs (AM1–5) in the pufferfish, Takifugu rubripes [2] and, as orthologs, AM2 and AM5 in mammals [3,4]. AM2 was identified at the same time by another group, and named intermedin [5].
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