Origins and metabolism of the intracellular amino acid pools in rat liver and muscle

Gan, Jose C.; Jeffay, Henry

doi:10.1016/0304-4165(67)90141-9

Cited by 201 publications

(43 citation statements)

References 12 publications

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“…In nonhibernating mammals protein synthetic rates undergo an initial decrease during the transition between the fed and postabsorptive states (Millward and Waterlow 1978;Li etal. 1979;McNurlan et al 1979) and then a further gradual decline which may result from decreased levels of mRNA (Millward and Waterlow 1978;Li et al 1979) and decreased degradative rates which lead to reduced availability of amino acids (Gan and Jeffay 1967;Cahill 1976). The hypothesis that protein metabolism might undergo changes during hibernation similar to those which have been observed in prolonged fasting in nonhibernators was tested by comparing bats aroused after 2 months of hibernation with summer bats after an overnight fast.…”

Section: Discussionmentioning

confidence: 99%

“…Since the hibernating bats used in this study had had no access to food for approximately 2 months, the amino acids used for protein synthesis must have come from the breakdown of existing proteins (see Gan and Jeffay 1967). Therefore, rates of protein degradation in hibernating bats should be equal to or greater than synthetic rates and the amount by which the degradative rate exceeds the synthetic rate should equal the rates of net protein loss.…”

Section: Discussionmentioning

confidence: 99%

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Protein metabolism in the pectoralis muscle and liver of hibernating bats,Eptesicus fuscus

Yacoe

1983

J Comp Physiol B

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Summary. Seasonal variations in protein metabolism of the pectoralis muscle and liver of the big brown bat, Eptesicus fuscus, are examined in relation to seasonal changes in physiological status. A technique is described for the determination of protein synthetic rates in vivo in animals too small for conventional methods. The results indicate no detectable rates of protein synthesis in hibernating bats during torpor bouts ( Table 2). Rates of synthesis in hibernating bats during periods of arousal are comparable to those of active summer bats (Table 2), despite the fact that the hibernating bats had not eaten in over 2 months. Rates of protein degradation were calculated from the rate of urea formation in torpid bats (Figs. 4, 5), the overall loss of pectoralis muscle and liver protein mass during hibernation (Table 3), the proportion of the total time of hibernation spent in torpor and arousal (Table 1), and the observed rates of protein synthesis (Table 2). These estimates (Table 4) indicate negligible rates of protein degradation in torpid bats. However, protein degradation during periodic arousals is comparable to that of summer bats after an overnight fast. These findings are consistent with earlier observations suggesting that significant gluconeogenesis from tissue protein occurs during spontaneous arousals from hibernation.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Protein metabolism in the pectoralis muscle and liver of hibernating bats,Eptesicus fuscus

Yacoe

1983

J Comp Physiol B

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“…The low specific radioactivity of intracellular AdoMet must be explained by the low specific activity of intracellular methionine. From permanent infusion experiments with lysine and tyrosine [14,15] it is known that the specific radioactivity of intracellular amino acid soon increased to a plateau value. However, even when the intracellular free amino acid pool was maximally labelled, the specific radioactivity was lower than that of plasma amino acid specific activity [14,15].…”

Section: Discussionmentioning

confidence: 99%

“…From permanent infusion experiments with lysine and tyrosine [14,15] it is known that the specific radioactivity of intracellular amino acid soon increased to a plateau value. However, even when the intracellular free amino acid pool was maximally labelled, the specific radioactivity was lower than that of plasma amino acid specific activity [14,15]. This observed intracellular dilution has been interpreted as being due to the catabolism of intracellular unlabelled protein.…”

Section: Discussionmentioning

confidence: 99%

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Monitoring of the Specific Radioactivity of S-Adenosylmethionine in Kidney in vivo

Stöcker¹,

Roos²,

Lange³

et al. 1977

Eur J Biochem

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The specific radioactivity of S-adenosylmethionine was followed in the cat kidney during the infusion of ~-[Me-~H]methionine into the corresponding renal artery. For this purpose l4C-labe1led 4-(2-aminoethyl)pyrocatechol( [14C]dopamine) as methyl acceptor was injected locally every 15 min and the 3H and 14C activity of the methylation product homovanillic acid, isolated fiom urine, was measured. Approximately 5 % of the 14C label is excreted during the first renal passage as ['4C]homovanillic acid. The specific activity of S-adeno~yl[Me-~H]methionine in the kidney was calculated from the known specific radioactivity of ['4C]dopamine injected and the measured radioactivity ratio, H : 14C, of homovanillic acid isolated from urine.The specific activity of S-adeno~yl[Me-~H]methionine reaches a constant value in kidney about 30-60 min after the beginning of the ~-[Me-~H]methionine infusion. This plateau value was 28 k 14% ( n = 5) lower than the specific activity of ~-[Me-~H]methionine in the venous blood from the corresponding kidney. The difference between the specific radioactivity of S-aden~syl[Me-~H]-methionine in kidney and of free methionine in plasma is explained by the existence of a methionine source of minor specific activity in the kidney. The average life span of S-adenosylmethionine in the kidney is 19.5 k 8.7 min (n = 5).

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Albumin

Tullis¹

1977

JAMA

120

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Origins and metabolism of the intracellular amino acid pools in rat liver and muscle

Cited by 201 publications

References 12 publications

Protein metabolism in the pectoralis muscle and liver of hibernating bats,Eptesicus fuscus

Protein metabolism in the pectoralis muscle and liver of hibernating bats,Eptesicus fuscus

Monitoring of the Specific Radioactivity of S-Adenosylmethionine in Kidney in vivo

Albumin

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