Document Detail

Fructose-6-phosphate substrate cycling and hormonal regulation of gluconeogenesis in vivo.
MedLine Citation:
PMID:  696824     Owner:  NLM     Status:  MEDLINE    
The possible role of the hepatic fructose-6-phosphate substrate cycle (phosphofructokinase, fructose-1,6-diphosphatase) in the rapid hormonal regulation of gluconeogenesis was investigated in vivo in fasted normal and adrenalectomized rats after administration of [3-3H, U-14C]- or [3-3H, 6-14C]glucose. The plasma glucose 3H/14C ratio was used as an index of substrate cycling because the amount of 3H loss from liver hexose phosphates is determined by the extent of cycling. PFK and FDPase activities limit 3H loss during gluconeogenesis and glycolysis, respectively. Glucagon-stimulated hepatic glucose production is always accompanied by increased substrate cycling, i.e., increased FDPase and PFK activities. The high PFK activity may be a secondary event due possibly to elevated cellular fructose-6-phosphate levels. Decreased substrate cycling, i.e., lowered FDPase activity, always accompanies the depressed hepatic glucose production that occurs during hyperglycemia. Glucagon has no effect on substrate cycling in adrenalectomized rats that are insensitive to the hormone. The in vivo experiments presented provide evidence, although indirect, that glucagon administration results in changes in the fructose-6-phosphate substrate cycle in a living animal. Whether these changes are primary regulatory events or occur secondarily to hormone actions elsewhere is not known.
M Chenoweth; A Dunn
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  235     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1978 Sep 
Date Detail:
Created Date:  1978-11-29     Completed Date:  1978-11-29     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  E295-303     Citation Subset:  IM    
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MeSH Terms
Adrenal Glands / physiology
Fructosephosphates / metabolism*
Glucagon / pharmacology*
Gluconeogenesis / drug effects*
Glucose / metabolism
Liver / metabolism*
Reg. No./Substance:
0/Fructosephosphates; 50-99-7/Glucose; 9007-92-5/Glucagon

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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