Figure 4. Effects of insulin and elevated D-glucose on cGMP accumulation and PGI₂ production in human umbilical vein endothelial cells isolated from gestational diabetic pregnancies.

Diabetic cells were cultured in M199 containing 20 % serum and either 5 mm (□) or 25 mm (▪) D-glucose in the absence or presence of human insulin (1 nM, 8 h). Cells were then washed and incubated in Krebs solution containing 0.5 mm IBMX, 100 μM L-arginine and either 5 or 25 mm D-glucose in the absence or presence of 1 nM insulin and/or 100 μM L-NAME. Accumulation of cGMP (A) and release of 6-keto-PGF_1α, a stable metabolite of PGI₂ (B), were then determined by radioimmunoassay (see Methods). The dotted line represents the basal rate of PGI₂ production in non-diabetic endothelial cells cultured in 5 mm D-glucose (see in Sobrevia et al. 1995a). Values denote the means ±s.e.m. of experiments in 4 different cell cultures. *P < 0.05.