L-Arginine transport and extracellular adenosine concentration.

(a) Overall (300 µmol/L) L-arginine transport in HUVECs cultured (8 hours) in absence (white bars) or presence (black bars) of 1 nmol/L insulin, without (–NBTI) or with (+NBTI) 10 µmol/L nitrobenzylthioinosine (NBTI). Cells were co-incubated in culture medium without (–) or with (+) CGS-21680 (30 nmol/L) or ZM-21385 (10 nmol/L). (b) L-Arginine transport in the absence or presence of NECA (10 nmol/L) or DPCPX (10 nmol/L) in cells as in (a). (c) Adenosine concentration in the culture medium in cells as in (a). *P<0.05 versus cells in the absence of NBTI, CGS-21680 and ZM-241385 (control). Values are mean ± SEM (n = 6–18).