Hormonal sensitivity and responsiveness in sea raven hepatocytes: changes with fasting and collagenase exposure

Foster, Glen D.; Moon, Thomas W.

doi:10.1139/z93-249

Cited by 12 publications

(5 citation statements)

References 24 publications

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“…showing similar effects in 6 week fasted sea raven (Foster and Moon 1993). The enhanced hepatocyte responsiveness to glucagon in the food-deprived sea raven ( Fig.…”

Section: Nutritional Effectssupporting

confidence: 55%

“…The enhanced hepatocyte responsiveness to glucagon in the food-deprived sea raven ( Fig. 2A) may mediate this increased glucose production (Foster and Moon 1993).…”

Section: Nutritional Effectsmentioning

confidence: 98%

“…This change in glucose production may have resulted from a decreased substrate mobilization or, alternatively, from an increased utilization of glucose. Foster and Moon (1993) showed that insulin had no effect on total glucose production, but prevented the increase in glucose production seen with glucagon in sea raven hepatocytes. Since cortisol also increased glucose production in this species, a similar mechanism of action (preventing the increase in glucose production) by insulin may be responsible for the lowered glucose production.…”

Section: Cortisol Effectsmentioning

confidence: 98%

“…The study also examines the role nutritional state may play in these cortisol actions. The sea raven, Hemitripterus americanus, a sit-and-wait marine predator was chosen as the experimental animal as the liver has been found to be a good model for examining hormonal effects on hepatic metabolism (Foster and Moon 1987, 1993.…”

Section: Introductionmentioning

confidence: 99%

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Effects of cortisol on hepatic carbohydrate metabolism and responsiveness to hormones in the sea raven, Hemitripterus americanus

Vijayan

Foster

Moon

1993

Fish Physiol Biochem

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The sea raven, Hemitripterus americanus, is a sit-and-wait, low metabolic rate, marine teleost. The objective of this study was to determine i) whether cortisol implantation (50 mg. kg(-1)) for 7 days altered hepatocyte metabolism, and hepatocyte responsiveness to epinephrine, glucagon and insulin, and ii) whether 8 weeks of food-deprivation modified the above response. Cortisol implantation significantly increased hepatocyte total glucose production and oxidation from alanine compared to the sham group. There was no cortisol effect on glycogen breakdown, suggesting that the activation of other pathways, including gluconeogenesis, are required to account for the increased glucose production. Epinephrine-mediated (10(-)5M) glycogen breakdown and insulin-mediated (10(-8)M) total glucose production were enhanced in hepatocytes of cortisol implanted sea ravens, but there were no change in any glucagon (10(-7)M) effects. The enhanced glycogen breakdown in the absence of similar increases in total glucose production with epinephrine indicates mobilization of carbohydrate reserves for endogenous use by the liver.Food-deprivation for 8 weeks significantly decreased condition factor, plasma cortisol concentration and liver glycogen content in the sea raven, but had no effect on plasma glucose concentration. Hepatocyte total glucose production and flux rates from alanine increased significantly with food-deprivation. Moreover, food-deprivation increased responsiveness of total hepatocyte glucose production to the actions of glucagon and insulin, but not to epinephrine; none of these effects were modified by cortisol implantation.Our results indicate that cortisol in the sea raven exerts both a direct and an indirect or permissive effect on hepatocyte metabolism by modifying hepatocyte responsiveness to epinephrine and insulin stimulation. Cortisol implantation did not modify the effects of glucagon or food-deprivation in this species.

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“…showing similar effects in 6 week fasted sea raven (Foster and Moon 1993). The enhanced hepatocyte responsiveness to glucagon in the food-deprived sea raven ( Fig.…”

Section: Nutritional Effectssupporting

confidence: 55%

“…The enhanced hepatocyte responsiveness to glucagon in the food-deprived sea raven ( Fig. 2A) may mediate this increased glucose production (Foster and Moon 1993).…”

Section: Nutritional Effectsmentioning

confidence: 98%

Section: Cortisol Effectsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effects of cortisol on hepatic carbohydrate metabolism and responsiveness to hormones in the sea raven, Hemitripterus americanus

Vijayan

Foster

Moon

1993

Fish Physiol Biochem

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“…Despite any negative effects that collagenase digestion might have on isolated cells, the advantages of its employment may outweigh its disadvantages. An alternative collagenase-free method of cell isolation used by Foster & Moon (1993) yielded sea raven hepatocytes with lower metabolic activity, and lower sensitivity and responsiveness to hormones than those isolated with collagenase. Ion levels, unfortunately were not investigated by these authors.…”

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confidence: 99%

Intracellular ion levels in erythrocytes and hepatocytes isolated from three teleost species

Furimsky

Perry

Moon

1999

Journal of Fish Biology

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Intracellular concentrations of Na + and K + were similar (75 mmol l 1 ) in rainbow trout Oncorhynchus mykiss hepatocytes directly following isolation by collagenase digestion, but partial recovery occurred over 6 h with K + levels increasing to 110 mmol l 1 and Na + levels decreasing to 42 mmol l 1 . Black bullhead Ameiurus melas hepatocytes exhibited higher intracellular concentrations of K + (90 mmol l 1 ) than Na + (55 mmol l 1 ) with no recovery occurring over 6 h following cell isolation. Concentrations of Na + , K + and Cl in eel Anguilla rostrata hepatocytes were similar (55 mmol l 1 ) following isolation, with no recovery occurring over time. Erythrocytes from all species apparently did not experience an intracellular ion imbalance following isolation as indicated by high K + levels (140 mmol l 1 ) and low Na + levels (<40 mmol l 1 ) during the entire 24-h monitoring period. Although hepatocytes from all species exhibited an ion imbalance post-isolation, comparison of their in vitro intracellular Na + and K + concentrations with those in plasma demonstrated that directionally correct ion gradients still exist across the cell membrane, albeit differing from those that would be found in the tissue in vivo. 1999 The Fisheries Society of the British Isles

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In vitro hepatocyte metabolism of alanine and glucose and the response to insulin in fed and fasted rainbow trout

1995

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Rainbow trout (Oncorhynchus mykiss) fasted for 4 months had lower plasma glucose concentration and hepatocyte glycogen content than the fed fish. Gluconeogenesis from alanine in the fasted fish was not significantly different from that of the fed fish, whereas both alanine glyconeogenesis and oxidation increased with fasting by 400% and 300%' respectively. Glyconeogenesis from glucose was not significantly different with fasting, whereas glucose oxidation decreased significantly with fasting. The presence of glucose (10 mM) in the medium did not modify alanine glyconeogenesis or gluconeogenesis in either the fed or the fasted groups. However, glucose did increase alanine oxidation in the fed group but not in the fasted group, this response being further stimulated in the presence of insulin. Alanine (2 mM) in the medium had no effect on glyconeogenesis from glucose in either fed or fasted trout hepatocytes. Insulin significantly decreased glucose oxidation in the fed fish, whereas the insulin effect on glucose oxidation in the fasted fish occurred only in the presence of alanine. The results indicate that nutritional state affects hepatocyte responsiveness to substrate utilization and insulin stimulation in trout. Specifically, the hepatocyte potential for glyconeogenesis is enhanced in the fasted fish, although this increased glycogen production is not due to an increased glucose utilization. o 1995 Wiley-Liss, Inc.

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Hormonal sensitivity and responsiveness in sea raven hepatocytes: changes with fasting and collagenase exposure

Cited by 12 publications

References 24 publications

Effects of cortisol on hepatic carbohydrate metabolism and responsiveness to hormones in the sea raven, Hemitripterus americanus

Effects of cortisol on hepatic carbohydrate metabolism and responsiveness to hormones in the sea raven, Hemitripterus americanus

Intracellular ion levels in erythrocytes and hepatocytes isolated from three teleost species

In vitro hepatocyte metabolism of alanine and glucose and the response to insulin in fed and fasted rainbow trout

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