THE EFFECTS OF 7-HOUR LOCAL HYPERGLYCEMIA ON FOREARM MACRO AND MICROCIRCULATORY BLOOD-FLOW AND VASCULAR REACTIVITY IN HEALTHY MAN

Animal studies suggest that hyperglycaemia directly affects local bloo d now and vascular reactivity. We studied the effects of 7 h of local forearm hyperglycaemia, on forearm (muscle) and skin microcirculatory blood now in 12 healthy men. Furthermore, the effects of this local hy perglycaemia on forearm vasoreactivity to noradrenaline were studied. Using the perfused forearm technique, a local hyperglycaemia of approx imately 16 mmol/l was induced by continuous intraarterial infusion of 5% glucose. All subjects received both glucose and placebo (0.9% Nacl) infusions on two different occasions, in random order and blinded for the subjects. Forearm (muscle) blood flow and vascular reactivity to noradrenaline were measured using venous occlusion plethysmography. Sk in microcirculatory blood flow was evaluated using intravital capillar y microscopy (nutritive blood now) and laser-Doppler fluxmetry (thermo regulatory blood flow). Measurements were performed at baseline, after 4 h, and after 7 h of intraarterial glucose or placebo infusion. Duri ng local glucose infusion there was a slight increase in the levels of insulin, C-peptide, systemic glucose, and blood pressure, compared to the placebo experiments. No differences were observed in forearm bloo d flow and laser-Doppler flux ratio (infused: contralateral arm), as w ell as in capillary blood cell velocity between glucose and placebo ex periments. Noradrenaline produced similar reductions in forearm blood flow ratio during glucose and placebo experiments. We conclude that in contrast to animal studies, local hyperglycaemia (approximate to 16 m mol/l) for 7 h does not affect forearm macro and microcirculatory bloo d flow or vascular reactivity to noradrenaline in man.