Transport of ascorbic acid and dehydroascorbic acid by pancreatic islet cells from neonatal rats
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Transport of ascorbic acid and dehydroascorbic acid by pancreatic islet cells from neonatal rats. / Zhou, A; Farver, O; Thorn, N A; Nielsen, Jens Høiriis.
In: Biochemical Journal, Vol. 274 ( Pt 3), 1991, p. 739-44.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Transport of ascorbic acid and dehydroascorbic acid by pancreatic islet cells from neonatal rats
AU - Zhou, A
AU - Farver, O
AU - Thorn, N A
AU - Nielsen, Jens Høiriis
PY - 1991
Y1 - 1991
N2 - Several amidated biologically active peptides such as pancreastatin, thyrotropin-releasing hormone, pancreatic polypeptide and amylin are produced in endocrine pancreatic tissue which contains the enzyme necessary for their final processing, i.e. peptidylglycine alpha-amidating mono-oxygenase (EC 1.14.17.3). The enzyme needs ascorbic acid for activity as well as copper and molecular oxygen. The present work shows that pancreatic islet cells prepared from overnight cultures of isolated islets from 5-7-day-old rats accumulate 14C-labelled ascorbic acid by a Na(+)-dependent active transport mechanism which involves a saturable process (estimated Km 17.6 microM). Transport was inhibited by ouabain, phloridzin, cytochalasin B, amiloride and probenecid. Glucose inhibited or stimulated uptake, depending on the length of incubation time of the cells. The uptake of dehydroascorbic acid was linearly dependent on concentration. Dehydroascorbic acid was converted to ascorbic acid by an unknown mechanism after uptake. The uptake of both ascorbic acid and dehydroascorbic acid was inhibited by tri-iodothyronine, and uptake of ascorbic acid, but not of dehydroascorbic acid, was inhibited by glucocorticoids. Isolated secretory granules contained a fairly low concentration of iron but a high concentration of copper.
AB - Several amidated biologically active peptides such as pancreastatin, thyrotropin-releasing hormone, pancreatic polypeptide and amylin are produced in endocrine pancreatic tissue which contains the enzyme necessary for their final processing, i.e. peptidylglycine alpha-amidating mono-oxygenase (EC 1.14.17.3). The enzyme needs ascorbic acid for activity as well as copper and molecular oxygen. The present work shows that pancreatic islet cells prepared from overnight cultures of isolated islets from 5-7-day-old rats accumulate 14C-labelled ascorbic acid by a Na(+)-dependent active transport mechanism which involves a saturable process (estimated Km 17.6 microM). Transport was inhibited by ouabain, phloridzin, cytochalasin B, amiloride and probenecid. Glucose inhibited or stimulated uptake, depending on the length of incubation time of the cells. The uptake of dehydroascorbic acid was linearly dependent on concentration. Dehydroascorbic acid was converted to ascorbic acid by an unknown mechanism after uptake. The uptake of both ascorbic acid and dehydroascorbic acid was inhibited by tri-iodothyronine, and uptake of ascorbic acid, but not of dehydroascorbic acid, was inhibited by glucocorticoids. Isolated secretory granules contained a fairly low concentration of iron but a high concentration of copper.
KW - Animals
KW - Animals, Newborn
KW - Ascorbic Acid
KW - Biological Transport
KW - Cytoplasmic Granules
KW - Dehydroascorbic Acid
KW - Glucocorticoids
KW - Glucose
KW - Ions
KW - Islets of Langerhans
KW - Metals
KW - Rats
KW - Rats, Inbred Strains
M3 - Journal article
C2 - 2012602
VL - 274 ( Pt 3)
SP - 739
EP - 744
JO - Biochemical Journal
JF - Biochemical Journal
SN - 0264-6021
ER -
ID: 299758