Endocrine Abstracts

C-type natriuretic peptide (CNP), the predominant natriuretic peptide in the pituitary, is associated with neuroendocrine development and function. Our previous studies show that genes encoding CNP (nppc2, cnp3, nppc4, and nppcl) are expressed during pituitary development in humans and zebrafish (Danio rerio), however a precise role for CNP in the pituitary has yet to be elucidated. Using the versatile zebrafish, we explored in vivo effects of exposing developing embryos to exogenous CNP. WT Tupfel long fin (TL) zebrafish embryos were collected from staged matings and exposed to 100 nM CNP-22 for 24, 48 or 72 hours post-fertilisation (hpf). Biometric analyses revealed a significant reduction in body length in embryos exposed to CNP across the developmental time course, along with a delayed onset of melanosome aggregation compared to untreated controls. Total RNA was subsequently extracted from treated and control embryos and simultaneous gene expression of the natriuretic peptide system in zebrafish (nppa (ANP), nppb (BNP), nppc2, cnp3, nppc4, nppcl (CNPs), npr1a, nprA (GC-A), nprB (GC-B), nprC (NPR3) corina (corin), furina and furinb (furins)) and phenotypic indicators of pituitary cell lineage (cga (α-subunit), gh1 (GH), pomca (proopiomelanocortin), pou1f1 (pit-1), smtlβ (somatolactin) and tshβ (thyroid stimulated hormone)) were examined using a multiplex qRT-PCR assay and GenomeLab GeXP analysis system. nppc4 was significantly decreased at 24 hpf (P<0.05) but increased at 48 hpf (P<0.01), whereas, nppcl was decreased at 48 and 72 hpf (P<0.01 and 0.05 respectively). Both npra and pomca were reduced at 48 hpf (P<0.05 and 0.01 respectively). To investigate the effects of elevated CNP exposure on cGMP accumulation, dispersed primary zebrafish embryo cultures were exposed to 100 nM CNP or ANP for up to 60 min. Both CNP and ANP increase cGMP accumulation over 60 min. Collectively, these data suggest that CNP has a role in the regulation of growth and pituitary gene expression during zebrafish development.