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Modulation of adenosine transport by insulin in human umbilical artery smooth muscle cells from normal or gestational diabetic pregnancies
Author(s) -
Aguayo Claudio,
Flores Carlos,
Parodi Jorge,
Rojas Romina,
Mann Giovanni E.,
Pearson Jeremy D.,
Sobrevia Luis
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.00243.x
Subject(s) - medicine , endocrinology , insulin , adenosine , glucose transporter , biology , chemistry
1 Adenosine transport was measured in human cultured umbilical artery smooth muscle cells, isolated from non‐diabetic or gestational diabetic pregnancies, under basal conditions and after pretreatment in vitro with insulin. 2 Adenosine transport in non‐diabetic smooth muscle cells was significantly increased by insulin (half‐maximal stimulation at 0.33 ± 0.02 n m , 8 h) and characterized by a higher maximal rate (V max ) for nitrobenzylthioinosine (NBMPR)‐sensitive ( es ) saturable nucleoside transport (17 ± 5 vs. 52 ± 12 pmol (μg protein) −1 min −1 , control vs. insulin, respectively) and maximal binding sites ( B max ) for [ 3 H]NBMPR (0.66 ± 0.07 vs. 1.1 ± 0.1 fmol (μg protein) −1 , control vs. insulin, respectively), with no significant changes in Michaelis‐Menten ( K m ) and dissociation ( K d ) constants. 3 In contrast, in smooth muscle cells from diabetic pregnancies, where the values of V max for adenosine transport (59 ± 4 pmol (μg protein) −1 min −1 ) and B max for [ 3 H]NBMPR binding (1.62 ± 0.16 fmol (μg protein) −1 ) were significantly elevated by comparison with non‐diabetic cells, insulin treatment (1 n m , 8 h) reduced the V max for adenosine transport and B max for [ 3 H]NBMPR binding to levels detected in non‐diabetic cells. 4 In non‐diabetic cells, the stimulatory effect of insulin on adenosine transport was mimicked by dibutyryl cGMP (100 n m ) and reduced by inhibitors of phosphatidylinositol 3‐kinase (10 n m wortmannin), nitric oxide synthase (100 μ m N G ‐nitro‐ l ‐arginine methyl ester, l ‐NAME) or protein synthesis (1 μ m cycloheximide), whereas inhibition of adenylyl cyclase (100 μ m SQ‐22536) had no effect. 5 Wortmannin or SQ‐22536, but not l ‐NAME or cycloheximide, attenuated the inhibitory action of insulin on the diabetes‐induced stimulation of adenosine transport. 6 Protein levels of inducible NO synthase (iNOS) were similar in non‐diabetic and diabetic cells, but were increased by insulin (1 n m , 8 h) only in non‐diabetic smooth muscle cells. 7 Our results suggest that adenosine transport via the es nucleoside transporter is modulated differentially by insulin in either cell type. Insulin increased adenosine transport in non‐diabetic cells via NO and cGMP, but inhibited the diabetes‐elevated adenosine transport via activation of adenylyl cyclase, suggesting that the biological actions of adenosine may be altered under conditions of sustained hyperglycaemia in uncontrolled diabetes.