Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1432-0428
    Keywords: Islets of Langerhans ; insulin ; glucose ; phosphoenolpyruvate ; substrate-site ; methylxanthines ; cyclic AMP ; calcium ; mitochondria ; fructose 1,6-diphosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 45Ca2+-accumulation by a mitochondrial fraction from isolated rat pancreatic islets was strongly stimulated by ATP. The ATP-dependent uptake was inhibited by phosphoenolpyruvate in a dose-dependent manner over a wide variety of conditions. Inhibition by phosphoenolpyruvate was noncompetitive with respect to calcium, competitive with respect to magnesium, and antagonised by high Mg-ATP2− concentrations; fructose 1,6-diphosphate also decreased 45Ca2+-uptake. Other glucose metabolites were either less effective or ineffective in diminishing mitochondrial 45Ca2+-accumulation. The ATP-dependent uptake was also inhibited by xanthine derivatives (caffeine and 3-isobutyl-l-methylxanthine) which potentiate the effects of glucose on insulin secretion. Cyclic AMP had no effect. It is thought that the rate of insulin secretion is a function of the cytosolic calcium concentration in the B-cell. These data show that phosphoenolpyruvate, fructose 1,6-diphosphate and methylxanthines might influence exocytosis by direct effects on mitochondrial calcium accumulation, and thus the intracellular distribution of calcium.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-0428
    Keywords: N-acetylglucosamine ; insulin release ; glyceraldehyde ; glucose ; glucosamine ; fructose ; galactose ; mannoheptulose ; glucoreceptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The specificity for carbohydrates of insulin secretory responses in vivo was studied. Test sugars were injected via a left femoral vein cannula into conscious rats. Blood samples collected over the ensuing 60 min via a left femoral arterial cannula were assayed for plasma insulin and glucose, and, in some experiments, for N-acetyl glucosamine. Whereas L-glucose or saline produced no significant changes in plasma insulin or glucose concentrations, D-glucose, N-acetylglucosamine, D-glucosamine, fructose, D-glyceraldehyde and DL-glyceraldehyde were potent secretagogues. Simultaneous injection of mannoheptulose abolished the insulin-otropic action of glucose and N-acetylglucosamine, but not of DL-glyceraldehyde. Fructose, glucosamine, and DL-glyceraldehyde induced hyperglycaemia, but peak insulin concentrations occurred before any change in plasma glucose concentration. No evidence was obtained for a stimulatory effect of galactose on insulin release. Infusion for 60 min of N-acetylglucosamine produced a sustained elevated plasma insulin concentration and significant hypoglycaemia. The present in vivo results agree with previous in vitro observations, and could indicate a role for sugars other than glucose in the regulation of insulin release.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 13 (1977), S. 481-486 
    ISSN: 1432-0428
    Keywords: Islets of Langerhans ; insulin ; glucose ; glyceraldehyde ; phosphoenolpyruvate ; glucoreceptor ; substrate-site ; regulator-site ; pyruvate kinase ; mannoheptulose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The content of phosphoenolpyruvate (PEP) has been measured in isolated rat islets of Langerhans incubated in vitro. Islet PEP was higher in islets incubated with 16.7 mmol/l glucose than in islets incubated with zero or 2.8 mmol/l glucose. Islet PEP content was also increased in islets incubated with 5 mmol/l D-glyceraldehyde. Mannoheptulose abolished the glucose-induced rise in PEP content but not that elicited by D-glyceraldehyde. These results are consistent with a role for PEP as an intracellular mediator of glucose- and glyceraldehyde-induced insulin release. The kinetics of pyruvate kinase in extracts of rat islets were studied. The maximal extractable activity was considerably higher than known rates of glycolytic flux. The Km values were found to be 0.16 mmol/l for PEP and 0.5 mmol/l for ADP. The control of islet PEP content and the possible role of PEP in insulin release are discussed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...