Dynamics of liver GH/IGF axis and selected stress markers in juvenile gilthead sea bream (Sparus aurata) exposed to acute confinement

Abstract

The time courses of liver GH/IGF axis and selected stress markers were analyzed in juvenile gilthead sea bream (Sparus aurata) sampled at zero time and at fixed intervals (1.5, 3, 6, 24, 72 and 120 h) after acute confinement (120 kg/m(3)). Fish remained unfed throughout the course of the confinement study, and the fasting-induced increases in plasma growth hormone (GH) levels were partially masked by the GH-stress inhibitory tone. Hepatic mRNA levels of growth hormone receptor-I (GHR-I) were not significantly altered by confinement, but a persistent 2-fold decrease in GHR-II transcripts was found at 24 and 120 h. A consistent decrease in circulating levels of insulin-like growth factor-I (IGF-I) was also found through most of the experimental period, and the down-regulated expression of GHR-II was positively correlated with changes in hepatic IGF-I and IGF-II transcripts. This stress-specific response was concurrent with plasma increases in cortisol and glucose levels, reflecting the cortisol peak (60-70 ng/mL), the intensity and duration of the stressor when data found in the literature were compared. Adaptive responses against oxidative damage were also found, and a rapid enhanced expression was reported in the liver tissue for mitochondrial heat-shock proteins (glucose regulated protein 75). At the same time, the down-regulated expression of proinflammatory cytokines (tumour necrosis factor-alpha) and detoxifying enzymes (cytochrome P450 1A1) might dictate the hepatic depletion of potential sources of reactive oxygen species. These results provide suitable evidence for a functional partitioning of hepatic GHRs under states of reduced IGF production and changing cellular environment resulting from acute confinement.

The response of brain serotonergic and dopaminergic systems to an acute stressor in rainbow trout: a time-course study

“…The dynamics of the response of several stress markers such as plasma cortisol or glucose after exposure to an acute stressor have been studied in fish (Aluru and Vijayan, 2006;Arends et al, 1999;Cockrem, 2013;Fast et al, 2008;Pickering et al, 1982;Saera-Vila et al, 2009;Small, 2004;Wilson et al, 1998). However, the first sampling time was usually performed 15 min or more post-stress.…”

Acclimation to different environmental salinities induces molecular endocrine changes in the GH/IGF-I axis of juvenile gilthead sea bream (Sparus aurata L.)

“…Even a co-incubation of hepatocytes with GH and cortisol could increase the hepatocyte IGF-I mRNA, despite the enhancement was less than that when incubating the hepatocytes with GH only (Pierce et al 2011). On the other hand, another type of stress, the confinement, could increase plasma cortisol levels in S. aurata, but decreased at the same time hepatic IGF-I mRNA expression, so cortisol/IGF-I interaction seems to be dependent also upon the stress situation (Saera-Vila et al 2009). Finally, the interaction may be also species dependent since the transfer of the Southern flounder Paralichthys lethostigma to seawater elevated plasma cortisol levels, but decreased hepatic IGF-I mRNA expression significantly (Tipsmark et al 2008).…”

Dietary oils mediate cortisol kinetics and the hepatic mRNA expression profile of stress-responsive genes in gilthead sea bream (Sparus aurata) exposed to crowding stress. Implications on energy homeostasis and stress susceptibility

“…At that point, three replicates from each dietary group (9-10 kg/m 3 ) remained undisturbed (control fish), whereas the remaining replicate was used as a donor tank of stressed fish, according to the protocol conducted in previous studies (Calduch-Giner et al, 2010;Saera-Vila et al, 2009b) and summarized in Fig. 1.…”

“…The coefficient of variation intra-and interassay was lower than 8% and 12%, respectively. Plasma glucose levels were measured by the glucose oxidase method (Thermo Electron, Louisville, CO, USA) as reported elsewhere (Bermejo-Nogales et al, 2007;Saera-Vila et al, 2009b as described earlier (Calduch-Giner et al, 2003). Briefly, RT reactions were conveniently diluted and the equivalent of 660 pg of total input RNA was used in a 25 µL volume for each PCR reaction.…”