Modulation by D-glucose anomers of the effect of D-fructose upon 45Ca efflux from prelabelled rat pancreatic islets.
It was recently reported that alpha-D-glucose is more potent than beta-D-glucose in conferring to glucokinase positive cooperativity towards D-fructose. We have now extended pilot experiments to investigate whether a comparable situation prevails in intact rat pancreatic islets in terms of the modulation by the D-glucose anomers of the effect of D-fructose upon 45Ca efflux from prelabelled perifused islets. As expected from the effect of increasing concentrations of equilibrated D-glucose upon 45Ca efflux from the prelabelled islets, D-fructose either decreased or increased 45Ca outflow from islets perifused in the presence of either alpha- or beta-D-glucose. In all cases, the alpha-anomer of D-glucose affected more markedly than beta-D-glucose the cationic response to D-fructose. These findings indicate that the anomeric specificity of the effect of D-glucose upon D-fructose phosphorylation by glucokinase is also operative in intact islets.
Jijakli
Hassan
H
Laboratory of Experimental Hormonology, Brussels Free University, 808 Route de Lennik, B-1070 Brussels, Belgium.
Zhang
Hai-Xia
HX
Sener
Abdullah
A
Malaisse
Willy J
WJ
D000818:Animals; D002132:Calcium Radioisotopes / Q000494:pharmacology*; D002412:Cations; D005260:Female; D005941:Glucokinase / Q000737:chemistry; D005947:Glucose / Q000737:chemistry*; D007515:Islets of Langerhans / Q000166:cytology / Q000473:pathology*; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D002132:Calcium Radioisotopes; D002412:Cations; D005941:Glucokinase; D005947:Glucose