Table 3.
Effects of insulin and elevated D-glucose on kinetics of L-arginine transport in umbilical vein endothelial cells isolated from gestational diabetic pregnancies
| Condition | Km (μM) | Vmax (pmol (μg protein)−1 min−1) | KD (pmol (μg protein)−1 min−1) | Vmax/Km |
|---|---|---|---|---|
| 5 mm D-glucose | 82 ± 34 | 9·0 ± 1·1 | 0·026 ± 0·003 | 0·11 ± 0·03 |
| 5 mm D-glucose + insulin | 74 ± 48 | 4·0 ± 0·7 * | 0·019 ± 0·002 | 0·05 ± 0·02 |
| 25 mm D-glucose | 86 ± 17 | 9·5 ± 0·5 | 0·026 ± 0·002 | 0·11 ± 0·01 |
| 25 mm D-glucose + insulin | 61 ± 41 | 8·3 ± 1·1 | 0·035 ± 0·005 | 0·14 ± 0·06 |
Diabetic endothelial cells were cultured in M199 containing 20 % serum and either 5 or 25 mm D-glucose in the absence or presence of 1 nM insulin added during the last 8 h of a 24 h incubation period. Cells were then incubated in Krebs solution and the kinetics of saturable L-arginine transport (1 min, 0·015-1 mm) determined in the presence of either 5 or 25 mm D-glucose and absence or presence of 1 nM insulin. Values denote the means ± s.e.m. of n = 4 different cell cultures
P < 0·02 relative to values in 5 or 25 mm D-glucose or 25 mm D-glucose + 1 nM insulin. All other Vmax values for L-arginine transport were significantly (P < 0·03) elevated compared with non-diabetic cells cultured in 5 mm D-glucose (Vmax = 4·9 ± 0·7, Km = 83 ± 11, KD= 0·018 ± 0·002, n = 4 paired experiments).