Different molecular forms of C-type natriuretic peptide isolated from the brain and heart of an elasmobranch, Triakis scyllia

in Journal of Endocrinology
Authors:
R. Suzuki
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A. Takahashi
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Y. Takei
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ABSTRACT

The presence of a C-type natriuretic peptide (CNP) has been reported in the brain of mammals, birds, amphibians and teleost fishes, mostly as a 22-residue peptide (CNP-22). In the present study, we attempted to isolate natriuretic peptides from an elasmobranch, Triakis scyllia, using a chick rectum-relaxant assay, and different molecular forms of CNP were found in the brain and heart. Only CNP-22 was recovered from the brain, as is the case in other vertebrates. A large amount of prohormone (proCNP or CNP-115) and small amounts of its C-terminal peptides (CNP-38 and CNP-39) were isolated from the atrium and ventricle, however. No CNP-22 was recovered from the heart. Natriuretic peptides other than CNP were not isolated from Triakis heart and brain by the rectumrelaxant assay. The 22 residues at the C-terminal region of proCNP, i.e. CNP-22, were well conserved when Triakis and mammals were compared, although the sequence homology of the N-terminal segment of proCNP was very low. Not only was CNP-22 identical but the N-terminal segments of proCNP were also quite similar when Triakis and another elasmobranch, Scyliorhinus canicula, were compared. These data suggest that, in elasmobranchs, CNP is a primary hormone in the natriuretic peptide family, and also that CNP is processed differently in the brain and heart.

Journal of Endocrinology (1992) 135, 317–323

 

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