Differential effects of a nitric oxide donor on reperfusion-induced microvascular dysfunction in diabetic and non-diabetic rats.

AIMS/HYPOTHESIS: Diabetes is associated with a high incidence of ischaemic disease and impaired nitric oxide responses. Therefore, the aim of the present study was to assess the effect of nitric oxide on ischaemia/reperfusion (I/R)-induced microvascular responses in an experimental model of diabetes.

METHODS

Leucocyte-endothelial cell interactions were studied in mesenteric venules after superior mesenteric artery occlusion (10 min), at 10 and 30 min of reperfusion in control and streptozotocin-induced diabetic rats. An oxidant-sensitive fluorochrome was used to measure oxidant production during reperfusion. P-selectin and ICAM-1 expression were quantified at 10 and 30 min of reperfusion respectively, using radiolabelled monoclonal antibodies. The transcription of ICAM-1 mRNA was determined by northern blot. The effect of spermine NONOate, given locally, on all variables studied, was assessed in additional experiments.

RESULTS

Ischaemia/reperfusion induced an enhanced leucocyte accumulation and oxidant production in diabetic animals. Moreover, I/R enhanced endothelial P-selectin expression in both groups of animals, whereas it only up regulated ICAM-1 endothelial expression and mRNA expression in diabetic rats. Spermine NONOate abrogated to a similar extent leucocyte adhesion and emigration in control and diabetic animals, although the mechanisms underlying this protective effect appear to be different. In control rats Spermine NONOate effectively prevented P-selectin up regulation, whereas in diabetic rats NO appreciably attenuated the rapid up regulation of ICAM-1 by preventing its transcription.

CONCLUSIONS/INTERPRETATION: Expression of ICAM-1 is rapidly increased in diabetic, but not control, animals exposed to I/R. The increased endothelial cell adhesion molecule expression, leucocyte-endothelial cell adhesion and oxidant stress induced by I/R in diabetic rats are significantly attenuated by exogenous NO. [Diabetologia (1999) 42: 1350-1358]