ISSN:
1432-0428
Keywords:
Monoamine oxidase
;
catechol-o-methyl-transferase
;
DL-threo-dihydroxyphenylserine
;
nor-epinephrine
;
pancreatic islets
;
reserpine
;
cate-cholamines
;
insulin secretion
;
fasting
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Using a specific and sensitive radioenzymatic assay that utilizes the partially purified enzyme phenylethanolamine-N-methyltransferase, studies were done to determine if pharmacological agents and/or fasting alter the norepinephrine concentration of collagenase-isolated golden hamster pancreatic islets. The norepinephrine concentration (42.1±8.07 μmol/kg net weight, mean±SEM) and the monoamine oxidase activity (5,407±530 pmol product /mg tissue/min) of hamster pancreatic islets was at least five times higher than acinar pancreas, kidney, heart, median eminence or cerebral cortex. The catechol-o-methyltransferase activity of hamster islets (7±2.3 pmol product/mg tissue/min) was one half or less than the other tissues. Islet norepinephrine was not increased by two days administration of the monoamine oxidase inhibitor tranylcypromine. Islet norepinephrine concentration was increased 2-fold by administration of the norepinephrine precursor DL-threo-dihydroxyphenylserine. This increase was enhanced by prior administration of tranylcypromine (3.5-fold) and prevented by prior administration of the decarboxylase inhibitor N1-(DL-seryl)-N2-(2,3,4-trihydroxybenzyl) hydrazine (RO-4-4602). There was a good correlation between the islet norepinephrine concentration and the plasma glucose concentration after pharmacological agents. Reserpine administration markedly depleted the islet norepinephrine concentra tion. Fasting of 24, 48 and 72 h did not alter the norepinephrine concentration in islets and heart. It is concluded that the pancreatic islets of the hamster have an active noradrenergic system, but that islet norepinephrine does not appear to play an important role in the impaired insulin secretion of fasting hamsters.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01219745
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