title: Perfused Gills Reveal Fundamental Principles of pH Regulation and Ammonia Homeostasis in the CephalopodOctopus vulgaris.
abstract: In contrast to terrestrial animals most aquatic species can be characterized by relatively higher blood [Formula: see text] concentrations despite its potential toxicity to the central nervous system. Although many aquatic species excrete [Formula: see text] via specialized epithelia little information is available regarding the mechanistic basis for NH3/[Formula: see text] homeostasis in molluscs. Using perfused gills ofOctopus vulgariswe studied acid-base regulation and ammonia excretion pathways in this cephalopod species. The octopus gill is capable of regulating ammonia (NH3/[Formula: see text]) homeostasis by the accumulation of ammonia at low blood levels (<260 μM) and secretion at blood ammonia concentrations exceedingin vivolevels of 300 μM. [Formula: see text] transport is sensitive to the adenylyl cyclase inhibitor KH7 indicating that this process is mediated through cAMP-dependent pathways. The perfused octopus gill has substantial pH regulatory abilities during an acidosis, accompanied by an increased secretion of [Formula: see text]. Immunohistochemical and qPCR analyses revealed tissue specific expression and localization of Na+/K+-ATPase, V-type H+-ATPase, Na+/H+-exchanger 3, and Rhesus protein in the gill. Using the octopus gill as a molluscan model, our results highlight the coupling of acid-base regulation and nitrogen excretion, which may represent a conserved pH regulatory mechanism across many marine taxa.
authors.affiliation: Institute of Physiology, University of KielKiel, Germany; Institute of Cellular and Organismic Biology, Academia SinicaTaipei, Taiwan.
authors.forename: Marian Y
authors.initials: MY
authors.lastname: Hu
authors.affiliation: Department of Life Science, National Taiwan University Taipei, Taiwan.
authors.forename: Po-Hsuan
authors.initials: PH
authors.lastname: Sung
authors.affiliation: Institute of Biological Chemistry, Academia Sinica Taipei, Taiwan.
authors.forename: Ying-Jey
authors.initials: YJ
authors.lastname: Guh
authors.affiliation: Institute of Cellular and Organismic Biology, Academia Sinica Taipei, Taiwan.
authors.forename: Jay-Ron
authors.initials: JR
authors.lastname: Lee
authors.affiliation: Institute of Cellular and Organismic Biology, Academia Sinica Taipei, Taiwan.
authors.forename: Pung-Pung
authors.initials: PP
authors.lastname: Hwang
authors.affiliation: Department of Biological Sciences, University of Manitoba Winnipeg, MB, Canada.
authors.forename: Dirk
authors.initials: D
authors.lastname: Weihrauch
authors.affiliation: Lab of Marine Organismic Physiology, Marine Research Station, Institute of Cellular and Organismic Biology, Academia Sinica Taipei, Taiwan.
authors.forename: Yung-Che
authors.initials: YC
authors.lastname: Tseng
keywords: NH3/NH4+ homeostasis; Na+/K+-ATPase; Rh-protein; acid-base regulation; cephalopod; invertebrate