Regulation of the rainbow trout (Oncorhynchus mykiss) hepatic β2-adrenoceptor by adrenergic agonists

Dugan, Stephen G.; Lortie, Michel B.; Nickerson, James G.; Moon, Thomas W.

doi:10.1016/s1096-4959(03)00217-3

Cited by 20 publications

(10 citation statements)

References 24 publications

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“…On the other hand, Dugan and Moon (1998) found no evidence of changes in hepatic membrane b-adrenoceptor numbers in cortisol-treated trout, nor did hepatocyte glucose production exhibit enhanced adrenergic responsiveness (Vijayan et al 1994;Dugan and Moon 1998). An added consideration is that repeated acute stress or exposure to adrenergic agonists decreased hepatic b-adrenoceptor numbers, although no effect on adrenergic responsiveness, measured as adenylyl cyclase activity, was detected (Dugan et al 2003). In this study, subordinate fish exhibited significantly fewer liver b-adrenoceptors than dominant fish.…”

Section: Discussionmentioning

confidence: 66%

“…As in previous studies (Mommsen et al 1988;Vijayan et al 1994;Van Heeswijk et al 2006), hepatocytes from all treatment groups responded to adrenaline with increased glucose production. However, despite differences in liver b-receptor numbers, hepatocytes from dominant and subordinate fish did not differ in the adrenergic responsiveness of glucose production in vitro, an outcome similar to that of Dugan et al (2003). At the same time, hepatocytes from cortisol-treated fish displayed increased adrenergic responsiveness of glucose production (relative to control fish) in the absence of any difference in liver b-adrenoceptor number.…”

Section: Discussionmentioning

confidence: 72%

“…Thus, in this study, hepatocyte adrenergic responsiveness was evaluated together with hepatic adrenoceptor characteristics and b 2 -adrenoceptor mRNA abundance. In previous work, hepatic b-adrenoceptors were downregulated by repeated acute stress or chronic exposure to adrenergic agonists (Dugan et al 2003), a response that presumably serves to minimize the effect of repeated stress on liver carbohydrate stores. Thus, it was predicted that adrenoceptor numbers and adrenergic responsiveness would be reduced in liver cells of subordinate trout.…”

Section: Introductionmentioning

confidence: 87%

“…Binding assays were carried out according to the methods of Dugan et al (2003) on tissues harvested from fish sampled in series II. Crude membranes were prepared from frozen livers as described by Dugan et al (2003), and membrane preparation protein content was determined by the bicinchoninic acid assay (Sigma) with BSA standards. Nonspecific binding was assessed in the presence of 10 mmol L Ϫ1 alprenolol, and 3 H-CGP-specific binding was then determined as the difference between total and nonspecific binding.…”

Section: Series Iii: Whole-liver B-adrenoceptorsmentioning

confidence: 99%

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The Influence of Social Status on Hepatic Glucose Metabolism in Rainbow TroutOncorhynchus mykiss

Gilmour

Kirkpatrick

Massarsky

et al. 2012

Physiological and Biochemical Zoology

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The effects of chronic social stress on hepatic glycogen metabolism were examined in rainbow trout Oncorhynchus mykiss by comparing hepatocyte glucose production, liver glycogen phosphorylase (GP) activity, and liver β-adrenergic receptors in dominant, subordinate, control, fasted, and cortisol-treated fish. Hepatocyte glucose production in subordinate fish was approximately half that of dominant fish, reflecting hepatocyte glycogen stores in subordinate trout that were just 16% of those in dominant fish. Fasting and/or chronic elevation of cortisol likely contributed to these differences based on similarities among subordinate, fasted, and cortisol-treated fish. However, calculation of the "glycogen gap"--the difference between glycogen stores used and glucose produced--suggested an enhanced gluconeogenic potential in subordinate fish that was not present in fasted or cortisol-treated trout. Subordinate, fasted, and cortisol-treated trout also exhibited similar GP activities (both total activity and that of the active or a form), and these activities were in all cases significantly lower than those in control trout, perhaps reflecting an attempt to protect liver glycogen stores or a modified capacity to activate GP. Dominant trout exhibited the lowest GP activities (20%-24% of the values in control trout). Low GP activities, presumably in conjunction with incoming energy from feeding, allowed dominant fish to achieve the highest liver glycogen concentrations (double the value in control trout). Liver membrane β-adrenoceptor numbers (assessed as the number of (3)H-CGP binding sites) were significantly lower in subordinate than in dominant trout, although this difference did not translate into attenuated adrenergic responsiveness in hepatocyte glucose production in vitro. Transcriptional regulation, likely as a result of fasting, was indicated by significantly lower β(2)-adrenoceptor relative mRNA levels in subordinate and fasted trout. Collectively, the data indicate that social status shapes liver metabolism and in particular glycogen metabolism, favoring accumulation of glycogen reserves from incoming energy in dominant fish and reliance on onboard fuels in subordinate fish.

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Section: Discussionmentioning

confidence: 66%

Section: Discussionmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 87%

Section: Series Iii: Whole-liver B-adrenoceptorsmentioning

confidence: 99%

See 2 more Smart Citations

The Influence of Social Status on Hepatic Glucose Metabolism in Rainbow TroutOncorhynchus mykiss

Gilmour

Kirkpatrick

Massarsky

et al. 2012

Physiological and Biochemical Zoology

Self Cite

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“…In protein metabolism, it may have an anabolic effect, hypertrophy of muscle fibers, and frequency changes in the type of muscle fibers (Beermann and Dunshea, 2005). Ractopamine has been tested in few species of fish, such as channel catfish Lovell, 1993, 1995) Dugan et al, 2003;Lortie et al, 2004;Haji-Abadi et al, 2010), pacu (Bicudo et al, 2012;Oliveira et al, 2014), and Hungarian carp (Devens et al, 2012). Thus, further studies are needed to test it in fishes of economic importance, such as the Nile tilapia, to determine the optimal dosage and time of supplementation.…”

Section: Introductionmentioning

confidence: 99%

Effect of ractopamine on Nile tilapia in the end of grow-out period

Tovo-Neto

Bittarello

Tovo³

et al. 2017

R. Bras. Zootec.

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-This experiment was conducted in outdoor tanks to evaluate the effect of inclusion of ractopamine at increasing levels (0, 4, 8, 12, and 16 mg kg −1 ) as additive in Nile tilapia (Oreochromis niloticus) diet in the final grow-out period (750-920 g) during 31 days. Therefore, 400 fish were housed into 20 experimental tanks, in a completely randomized design with five treatments and four replications. Growth performance, body yield, and chemical composition of fish muscle and organs were evaluated. Fish fed diets containing up to 16 mg kg −1 of ractopamine for 31 days did not improve growth or performance parameters. However, lipid percentage of abdominal muscle was different in fish fed ractopamine, reaching the lowest level of 199.3 g kg −1 of ether extract at 8 mg kg −1 treatment. Other body chemical composition parameters did not differ between animals treated or not treated. Feeding ractopamine up to 31 days has limited effect on body composition in Nile tilapia (~900 g), without any changes in growth parameters. This is a lower metabolic response in this species when compared with mammals and other terrestrial animals.

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