Intraluminal hyperglycaemia causes conduit and resistance artery dilatation and inhibits vascular autoregulation in the anaesthetised pig

Therese Ruane-O’Hora, Christine M. Shortt, Deirdre Edge, Farouk Markos, Mark I.M. Noble

The effect of intraluminal hyperglycaemia was investigated in the iliac artery of 11 anaesthetised pigs. Following isolation of a test segment, hyperglycaemic blood (40 mmol·L(-1)) caused a significant dilatation of the artery of 167 ± 208 μm (mean ± SD; n = 6, P = 0.031). Dilatations were reduced by N(G)-nitro-l-arginine methyl esther (250 μg·mL(-1)) from 145 ± 199 to 38 ± 5 μm), but this was not statistically significant (n = 6, P = 0.18). Intra-arterial infusions of d-glucose (20-40 mmol·L(-1)·min(-1)), during graded constrictions, caused statistically significant increases in blood flow (n = 11, P = 0.0013). Vasodilatation was confirmed by measurements of the ratio of immediate pressure steps to flow steps (∂P/∂F) during the graded obstruction experiments, showing a decrease in instantaneous vascular resistance from a control of 0.62 ± 0.30 to 0.33 ± 0.34 mm Hg·mL(-1)·min(-1) (n = 7, P = 0.016). Autoregulation was assessed from the slopes of the plots of steady-state flow versus pressure. There were significant increases in the slope from 2.32 ± 1.03 to 5.88 ± 5.60 mL·min(-1)·(mm Hg)(-1) (n = 7, P = 0.0078), indicating significant impairment of autoregulation. In conclusion, luminal hyperglycaemia relaxes both arterial and resistance vessel smooth muscle.