Insulin Restores Gestational Diabetes Mellitus–Reduced Adenosine Transport Involving Differential Expression of Insulin Receptor Isoforms in Human Umbilical Vein Endothelium

OBJECTIVE—To determine whether insulin reverses gesta-tional diabetes mellitus (GDM)–reduced expression and activity of human equilibrative nucleoside transporters 1 (hENT1) in hu-man umbilical vein endothelium cells (HUVECs). RESEARCH DESIGN AND METHODS—Primary cultured HUVECs from full-term normal (n = 44) and diet-treated GDM (n = 44) pregnancies were used. Insulin effect was assayed on hENT1 expression (protein, mRNA, SLC29A1 promoter activity) and activity (initial rates of adenosine transport) as well as endo-thelial nitric oxide (NO) synthase activity (serine1177 phosphory-lation, L-citrulline formation). Adenosine concentration in culture medium and umbilical vein blood (high-performance liquid chro-matography) as well as insulin receptor A and B expression (quantitative PCR) were determined. Reactivity of umbilical vein rings to adenosine and insulin was assayed by wire myography