Figure 3. Effects of insulin and elevated D-glucose on L-arginine transport in umbilical vein endothelial cells isolated from gestational diabetic pregnancies.

Diabetic cells were cultured in M199 containing either 5 or 25 mm D-glucose in the presence or absence of human insulin (0.1-10 nM, 8 h). In A, L-arginine transport (100 μM, 1 min) was then measured in cells incubated in Krebs solution containing either 5 mm (^) or 25 mm (•) D-glucose and the specified concentrations of human insulin. The dotted line represents the concentration-dependent stimulation of L-arginine transport in non-diabetic umbilical vein endothelial cells cultured in 5 mm D-glucose (see Fig. 1A in Sobrevia et al. 1996). B, effects of cycloheximide (17 μM, 24 h) on L-arginine transport (100 μM, 1 min) in diabetic endothelial cells pretreated with 5 mm (□) or 25 mm (▪) D-glucose in the absence or presence of 1 nM insulin (8 h). Values denote the means ±s.e.m. of 3 different cell cultures. *P < 0.05 relative to all other values.