Expression of glucose transporter-2, glucokinase and mitochondrial glycerolphosphate dehydrogenase in pancreatic islets during rat ontogenesis.
To gain better insight into the insulin secretory activity of fetal beta cells in response to glucose, the expression of glucose transporter 2 (GLUT-2), glucokinase and mitochondrial glycerol phosphate dehydrogenase (mGDH) were studied. Expression of GLUT-2 mRNA and protein in pancreatic islets and liver was significantly lower in fetal and suckling rats than in adult rats. The glucokinase content of fetal islets was significantly higher than of suckling and adult rats, and in liver the enzyme appeared for the first time on about day 20 of extrauterine life. The highest content of hexokinase I was found in fetal islets, after which it decreased progressively to the adult values. Glucokinase mRNA was abundantly expressed in the islets of all the experimental groups, whereas in liver it was only present in adults and 20-day-old suckling rats. In fetal islets, GLUT-2 and glucokinase protein and their mRNA increased as a function of increasing glucose concentration, whereas reduced mitochondrial citrate synthase, succinate dehydrogenase and cytochrome c oxidase activities and mGDH expression were observed. These findings, together with those reported by others, may help to explain the decreased insulin secretory activity of fetal beta cells in response to glucose.
García-Flores
Marta
M
Department of Biochemistry and Molecular Biology, Faculty of Medicine, Complutense University, Madrid, Spain.
Zueco
José Antonio
JA
Arenas
Joaquín
J
Blázquez
Enrique
E
D000818:Animals; D005260:Female; D005333:Fetus / Q000378:metabolism*; D005941:Glucokinase / Q000096:biosynthesis* / Q000235:genetics; D005947:Glucose / Q000494:pharmacology; D051273:Glucose Transporter Type 2; D005993:Glycerolphosphate Dehydrogenase / Q000096:biosynthesis* / Q000235:genetics; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism*; D008297:Male; D008928:Mitochondria / Q000201:enzymology*; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis* / Q000235:genetics; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar
D051273:Glucose Transporter Type 2; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; D005993:Glycerolphosphate Dehydrogenase; D005941:Glucokinase; D005947:Glucose