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Diabetes‐induced activation of system y+ and nitric oxide synthase in human endothelial cells: association with membrane hyperpolarization.
Author(s) -
Sobrevia L,
Cesare P,
Yudilevich D L,
Mann G E
Publication year - 1995
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 - 10.1113/jphysiol.1995.sp021040
Subject(s) - medicine , endocrinology , umbilical vein , nitric oxide , prostacyclin , arginine , hyperpolarization (physics) , nitric oxide synthase , chemistry , membrane potential , biology , biochemistry , in vitro , amino acid , organic chemistry , nuclear magnetic resonance spectroscopy
1. The activity of the human endothelial cell L‐arginine transporter (system y+) has been correlated with cGMP production (index of nitric oxide) and prostacyclin (PGI2) release in umbilical vein endothelial cells cultured from normal or gestational diabetic pregnancies. 2. In non‐diabetic and diabetic cells, transport of L‐arginine was Na+ and pH independent, inhibited by other cationic L‐arginine analogues and unaffected by neutral amino acids. 3. Diabetes was associated with an increased Vmax for saturable L‐arginine transport (4.6 +/‐ 0.13 vs. 9.9 +/‐ 0.5 pmol (microgram protein)‐1 min‐1, P < 0.01), but had no effect on initial rates of transport for L‐serine, L‐citrulline, L‐leucine or 2‐deoxyglucose. 4. In non‐diabetic and diabetic cells, elevated K+ resulted in a concentration‐dependent inhibition in the initial rates of transport for L‐arginine and the membrane potential‐sensitive probe tetra[3H]phenylphosphonium (TPP+). 5. When resting membrane potential was measured using the whole‐cell patch voltage clamp technique, diabetic cells were hyperpolarized (‐78 +/‐ 0.3 mV) compared with non‐diabetic cells (‐70 +/‐ 0.04 mV, P < 0.04). Accumulation of [3H]TPP+ was also increased in diabetic compared with non‐diabetic cells. 6. Basal intracellular cGMP levels were elevated 2.5‐fold in diabetic cells, and L‐NAME (100 microM), an inhibitor of nitric oxide synthase, abolished basal cGMP accumulation in non‐diabetic and diabetic cells. 7. Histamine (10 microM) had no effect on L‐arginine transport but evoked significant increases in cGMP in non‐diabetic and diabetic cells, which were completely inhibited by L‐NAME but unaffected by superoxide dismutase. 8. Basal and histamine‐stimulated PGI2 release was decreased markedly in diabetic cells. 9. Our findings demonstrate that gestational diabetes is associated with phenotypic changes in fetal endothelial cells, which result in a membrane hyperpolarization, activation of the human endothelial cell L‐arginine transporter (system y+), elevation of basal nitric oxide synthesis and decreased PGI2 production.