title: Salinity-dependent in vitro effects of homologous natriuretic peptides on the pituitary-interrenal axis in eels.
abstract: We examined the effects of atrial, B-type, ventricular and C-type natriuretic peptides (ANP, BNP, VNP and CNP1, 3, 4) on cortisol secretion from interrenal tissue in vitro in both freshwater (FW) and seawater (SW)-acclimated eels. We first localized the interrenal and chromaffin cells in the eel head kidney using cell specific markers (cholesterol side-chain cleavage enzyme (P450ssc) and tyrosine hydroxylase (TH), respectively) and established the in vitro incubation system for eel interrenal tissue. Unexpectedly, none of the NPs given alone to the interrenal tissue of FW and SW eels stimulated cortisol secretion. However, ANP and VNP, but not BNP and three CNPs, enhanced the steroidogenic action of ACTH in SW interrenal preparations, while CNP1 and CNP4, but not ANP, BNP, VNP and CNP3, potentiated the ACTH action in FW preparations. These salinity dependent effects of NPs are consistent with the previous in vivo study in the eel where endogenous ACTH can act with the injected NPs. 8-Br-cGMP also enhanced the ACTH action in both FW and SW eel preparations, suggesting that the NP actions were mediated by the guanylyl cyclase-coupled NP receptors (GC-A and B) that were localized in the eel interrenal. Further, ANP and CNP1 stimulated ACTH secretion from isolated pituitary glands of SW and/or FW eels. In summary, the present study revealed complex mechanisms of NP action on corticosteroidogenesis through the pituitary-interrenal axis in eels, thereby providing a deeper insight into the role of the NP family in the acclimation of this euryhaline teleost to diverse salinity environments.
authors.affiliation: Laboratory of Physiology, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan. ventura@aori.u-tokyo.ac.jp
authors.forename: Albert
authors.initials: A
authors.lastname: Ventura
authors.forename: Makoto
authors.initials: M
authors.lastname: Kusakabe
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Takei
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology; D019439:Chromaffin Cells / Q000187:drug effects / Q000378:metabolism; D060226:Head Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006854:Hydrocortisone / Q000378:metabolism; D007401:Interrenal Gland / Q000187:drug effects* / Q000378:metabolism; D020097:Natriuretic Peptide, Brain / Q000494:pharmacology; D020098:Natriuretic Peptide, C-Type / Q000494:pharmacology; D045265:Natriuretic Peptides / Q000494:pharmacology*; D010902:Pituitary Gland / Q000187:drug effects* / Q000378:metabolism; D011863:Radioimmunoassay
chemical_list: D045265:Natriuretic Peptides; D020097:Natriuretic Peptide, Brain; D020098:Natriuretic Peptide, C-Type; D009320:Atrial Natriuretic Factor; D006854:Hydrocortisone