In vitro stimulation of hepatic glycogen phosphorylase activity by epinephrine and glucagon in the killifish, Fundulus heteroclitus

Umminger, Bruce L.; Benziger, David P.; Levy, S. W.

doi:10.1016/0306-4492(75)90047-7

Cited by 7 publications

(7 citation statements)

References 12 publications

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“…Even though the animals used in this study are 6-8 months starved (a condition experienced in nature by eels) these values are consistent with other liver GPase studies in catfish (Umminger and Benziger 1975;Ottolenghi et al 1986Ottolenghi et al , 1988, goldfish (Storey 1988) and rat (e.g. Schwartz and Rall 1973;Stalman and Hers 1975;Katz et al 1979).…”

Section: Discussionsupporting

confidence: 74%

“…The inositol-P mechanism in the rat liver takes precedence at low hormone concentrations (10-10 to 10-8 M). The contrasting effects of glucagon found in this study compared to previous studies where significant effects of glucagon on GPase were noted (Umminger and Benziger 1975;Vernier and Sire 1978;Ottolenghi et al 1988) may be related to the lower concentration of hormone employed in our study (10-8 M), where inositol-P may be the second messenger. In fact, we found that anglerfish glucagon did not increase hepatocyte cAMP content at concentrations below 10 -7 M, whereas significant effects of the hormone on glucose production were apparent at hormone concentrations as low as 10 -9 M. Similar concentration-dependent effects on glycogenolysis have been found in goldfish, Carassius auratus, hepatocytes (Birnbaum et al 1976).…”

Section: Discussioncontrasting

confidence: 56%

“…This may indicate that in other studies (e.g. Umminger and Benziger 1975;Vernier andSire 1978a, 1978b;Ottolenghi et al 1986) GPase a activities had been overestimated. Both agents should be included for accurate estimates of this enzyme.…”

Section: Discussionmentioning

confidence: 65%

“…Glucagon stimulates liver GPase activities in catfish (Umminger and Benziger 1975;Ottolenghi et al 1988), trout (Vernier and Sire 1978), and killifish , and this is associated with a decrease in glycogen content in catfish liver pieces or slices (Umminger and Benziger 1975;Ottolenghi et al 1988). Glycogen content is also decreased by bovine glucagon in hepatocytes of the sea raven (Foster and Moon 1987) and the American eel this study).…”

Section: Discussionmentioning

confidence: 71%

“…Intered in the liver of trout (Salmo gairdneri : Vernier and Sire 1978), catfish (Ictalurus sp. : Ottolenghi et al 1986Ottolenghi et al , 1988, killifish (Fundulus heteroclitus: Umminger and Benziger 1975;, and salmon (Oncorhynchus tshawytcha, 0. kisutch: Plisetskaya et al 1989). Epinephrine, however, did not alter GPase activities in the liver of the carp (Cyprinus carpio) (Demael-Suard and Garin 1970), a fish that contains an amylase with activities exceeding that of GPase (Murat 1976;Pikucans and Umminger 1979).…”

Section: Introductionmentioning

confidence: 99%

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The role of glycogen phosphorylase in the regulation of glycogenolysis by insulin and glucagon in isolated eel (Anguilla rostrata) hepatocytes

Foster

Moon

1990

Fish Physiol Biochem

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The effects of porcine, scombroid, and salmon insulins, and bovine and anglerfish glucagons on glycogen depletion and glycogen phosphorylase (GPase) activities were examined in freshly isolated American eel (Anguilla rostrata) hepatocytes. Eel liver GPase in crude homogenates was activated (increase in % GPase a) by phosphorylating conditions and was rapidly inactivated (less than 1 h) when a phosphatase inhibitor (fluoride) was absent. Caffeine inhibits, and AMP activates, the b form of GPase consistent with their effects on rat liver GPase. Both mammalian and fish glucagons increased glucose production in eel hepatocytes, but had more ambiguous effects on glycogen levels and GPase activities. The magnitude of bovine glucagon effects were dependent on the initial glycogen content of the cells; only at glycogen concentrations less than approximately 70 μmoles.g(-1) did glucagon significantly increase % GPase a. Anglerfish glucagon significantly increased cyclic AMP (cAMP) concentrations by 90% at 10(-7) M, but had no effects at 10(-9) M and 10(-8) M. Scombroid and salmon insulins maintained hepatocyte glycogen concentrations and decreased glucose production, with these effects more pronounced at low (10(-9) to 10(-8) M) rather than high (10(-7) M) hormone concentrations. Porcine and salmon insulins decreased total GPase and % GPase a activities, and salmon insulin decreased CAMP levels, but only at 10(-8) M (by 44%).Glycogen is, therefore, depleted by glucagon and maintained by insulin in freshly isolated American eel hepatocytes, and these changes are accomplished, at least in part, by changes in the activities of GPase. Changes in cAMP do not explain all of the observed hormone effects.

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