title: β-Adrenergic regulation of Na+ uptake by larval zebrafish Danio rerio in acidic and ion-poor environments.
abstract: The potential role of adrenergic systems in regulating Na(+) uptake in zebrafish (Danio rerio) larvae was investigated. Treatment with isoproterenol (a generic β-adrenergic receptor agonist) stimulated Na(+) uptake, whereas treatment with phenylephrine (an α(1)-adrenergic receptor agonist) as well as clonidine (an α(2)-adrenergic receptor agonist) significantly reduced Na(+) uptake, suggesting opposing roles of α- and β-adrenergic receptors in Na(+) uptake regulation. The increase in Na(+) uptake associated with exposure to acidic water (pH = 4.0) was attenuated in the presence of the nonselective β-receptor antagonist propranolol or the β(1)-receptor blocker atenolol; the β(2)-receptor antagonist ICI-118551 was without effect. The stimulation of Na(+) uptake associated with ion-poor water (32-fold dilution of Ottawa tapwater) was unaffected by β-receptor blockade. Translational gene knockdown of β-receptors using antisense oligonucleotide morpholinos was used as a second method to assess the role of adrenergic systems in the regulation of Na(+) uptake. Whereas β(1)- or β(2B)-receptor knockdown led to significant decreases in Na(+) uptake during exposure to acidic water, only β(2A)-receptor morphants failed to increase Na(+) uptake in response to ion-poor water. In support of the pharmacology and knockdown experiments that demonstrated an involvement of β-adrenergic systems in the control of Na(+) uptake, we showed that the H(+)-ATPase-rich (HR) cell, a subtype of ionocyte known to be a site of Na(+) uptake, is innervated and appears to express β-adrenergic receptors (propranolol binding sites) at 4 days postfertilization. These data indicate an important role of adrenergic systems in regulating Na(+) uptake in developing zebrafish.
authors.affiliation: Dept. of Biology, Univ. of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kumai
authors.forename: Mellissa A R
authors.initials: MA
authors.lastname: Ward
authors.forename: Steve F
authors.initials: SF
authors.lastname: Perry
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D002395:Catecholamines; D006854:Hydrocortisone; D006863:Hydrogen-Ion Concentration; D007477:Ions; D007814:Larva; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D014867:Water / Q000737:chemistry; D015027:Zebrafish
chemical_list: D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D002395:Catecholamines; D007477:Ions; D011943:Receptors, Adrenergic, beta; D014867:Water; D012964:Sodium; D006854:Hydrocortisone