title: GH, IGF-I and GH receptors mRNA expression in response to growth impairment following a food deprivation period in individually housed cichlid fish Cichlasoma dimerus.
abstract: Cichlasoma dimerus is a social cichlid fish capable of growing at high rates under laboratory conditions, but knowledge on somatic growth regulation is still unclear. Growth hormone (GH)/insulin-like growth factor I (IGF-I) axis is the key regulator of somatic growth in vertebrates. Two types of growth hormone receptors have been described in teleost fish, named GH receptor type 1 (GHR1) and type 2 (GHR2). In addition, isoforms of these receptors lacking part of the intracellular region have been described. The aim of this study was to evaluate the somatic growth, liver histology and changes in the GH/IGF-I axis after 4 weeks of food deprivation in C. dimerus. Four-week fasted fish showed reductions in specific growth rates in body weight (p < 0.001) and standard length (p < 0.001). Additionally, the hepatosomatic index (p < 0.001) and hepatocyte area (p < 0.001) decreased in fasted fish, while no changes in glucose levels were detected in plasma. The starvation protocol failed to induce changes in GH mRNA levels in the pituitary and IGF-I mRNA levels in liver. In contrast, IGF-I mRNA levels in muscle decreased in fasted fish (p = 0.002). On the other hand, GHR2 (detected with primer sets designed over the extracellular and intracellular region) was upregulated by starvation both in liver and muscle (p < 0.05), while GHR1 remained unchanged. These results show that a fasting period reduced somatic growth both in length and body weight concomitantly with alterations on liver and muscle GHR2 and muscle IGF-I mRNA expression.
authors.affiliation: Laboratorio de Neuroendocrinología del Crecimiento y la Reproducción, DBBE, FCEN-UBA, Ciudad Universitaria, C1428EGA, Buenos Aires, Argentina.
authors.forename: Tomás Horacio
authors.initials: TH
authors.lastname: Delgadin
authors.forename: Daniela Irina
authors.initials: DI
authors.lastname: Pérez Sirkin
authors.forename: María Paula
authors.initials: MP
authors.lastname: Di Yorio
authors.forename: Silvia Eda
authors.initials: SE
authors.lastname: Arranz
authors.forename: Paula Gabriela
authors.initials: PG
authors.lastname: Vissio
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001483:Base Sequence; D049628:Body Size / Q000502:physiology; D023681:Cichlids / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D005508:Food Deprivation / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D013006:Growth Hormone / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D011986:Receptors, Somatotropin / Q000378:metabolism*; D017422:Sequence Analysis, DNA
chemical_list: D017931:DNA Primers; D012333:RNA, Messenger; D011986:Receptors, Somatotropin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone