Induction and decay of amino acid transport in the liver. Turnover of transport activity in isolated hepatocytes after stimulation by diabetes or glucagon.

Handlogten ME, Kilberg MS

The Journal of biological chemistry1 Mar 1984Cited by 55 (Europe PMC)

PMID6200477DOI10.1016/s0021-9258(17)43125-5PepBankPUB-06200477

Publisher page PubMedAsk about this study

Summary

System A-mediated amino acid transport in liver tissue is stimulated by diabetes or by exogenous glucagon. The present report describes the decay process for stimulated System A activity in isolated rat hepatocytes. Transport induced by glucagon, insulin, or spontaneous diabetes (BB/G rats) decayed rapidly after initiation of primary cultures; the estimated half-life was about 1.5 h. In contrast, the stimulated activity in cultured hepatocytes from streptozotocin-diabetic rats had a half-life of about 2.5 h. It is not known if the loss of System A activity is the result of proteolysis or of another form of inactivation. The decay was blocked by either actinomycin or cycloheximide, but was unaffected by leupeptin, methylamine, chloroquine, dinitrophenol, rotenone, or tunicamycin. Studies with cycloheximide and actinomycin suggest the following: 1) within 30 min after initiation of cell cultures, synthesis of the corresponding mRNA for the transport-inactivating protein has begun; 2) the mRNA for transport-inactivating protein is relatively long-lived, but the inactivating protein itself has a half-life of less than 1 h; and 3) actinomycin blocks the decay through inhibition of transport-inactivating protein biosynthesis rather than by protection of the mRNA for the protein responsible for System A activity. A working model for the synthesis and decay of System A activity is presented. Cationic amino acid transport, System y+, was also stimulated severalfold after induction of diabetes or glucagon injection of rats. Systems ASC, X-, and N were enhanced to varying degrees in hepatocytes from diabetic or glucagon-injected rats, but the level of stimulation for each was not as great as that found for Systems A or y+.

CC BYText from Europe PMC. Highlighted sentences are the source of results.

Results from this study2

2 results from studies that gave the peptide. No result from this study comes from people.

01AnimalAnimal study (in vivo)Mechanism
In rats, glucagon injection stimulated cationic amino acid transport System y+ severalfold.
In plain wordsIn rats, glucagon injection increased liver cell transport of positively charged amino acids severalfold.
Peptide
Glucagon
Outcome
IncreaseSystem y+ amino acid transport
Study
ratn: not reported in source
Hepatocytes collected from glucagon-injected rats
Outcome group
Amino Acid Transport · Liver
Studied dose
Dose not stated · injectionAs given in this study (rat).
Source sentences
Summary
Cationic amino acid transport, System y+, was also stimulated severalfold after induction of diabetes or glucagon injection of rats.
Show in the study text Report a problemFND-0620047701
02AnimalAnimal study (in vivo)Mechanism
In rats, glucagon injection enhanced hepatocyte Systems ASC, X-, and N to varying degrees, less than Systems A or y+.
In plain wordsIn rats, glucagon injection increased three liver cell amino acid transport systems less than Systems A or y+.
Peptide
Glucagon
Outcome
IncreaseSystems ASC, X-, and N amino acid transport
Study
ratn: not reported in source
Hepatocytes collected from glucagon-injected rats
Outcome group
Amino Acid Transport · Liver
Studied dose
Dose not stated · injectionAs given in this study (rat).
Source sentences
Summary
Systems ASC, X-, and N were enhanced to varying degrees in hepatocytes from diabetic or glucagon-injected rats, but the level of stimulation for each was not as great as that found for Systems A or y+.
1 context sentence(design, population, supporting numbers)
Summary · context
Cationic amino acid transport, System y+, was also stimulated severalfold after induction of diabetes or glucagon injection of rats.
Show in the study text Report a problemFND-0620047702

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Version history

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Version 2Current
28 Oct 2026, 02:03 UTC
Study results updated
Version 1
27 Oct 2026, 16:35 UTC
First added · source update from Europe PMC

Subjects

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