The effects of 7-hour local hyperglycaemia on forearm macro and microcirculatory blood flow and vascular reactivity in healthy man.

Animal studies suggest that hyperglycaemia directly affects local blood flow and vascular reactivity. We studied the effects of 7 h of local forearm hyperglycaemia, on forearm (muscle) and skin microcirculatory blood flow in 12 healthy men. Furthermore, the effects of this local hyperglycaemia on forearm vasoreactivity to noradrenaline were studied. Using the perfused forearm technique, a local hyperglycaemia of approximately 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. Skin microcirculatory blood flow was evaluated using intravital capillary microscopy (nutritive blood flow) and laser-Doppler fluxmetry (thermoregulatory blood flow). Measurements were performed at baseline, after 4 h, and after 7 h of intraarterial glucose or placebo infusion. During 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 blood flow and laser-Doppler flux ratio (infused: contralateral arm), as well as in capillary blood cell velocity between glucose and placebo experiments. Noradrenaline produced similar reductions in forearm blood flow ratio during glucose and placebo experiments. We conclude that in contrast to animal studies, local hyperglycaemia (approximately 16 mmol/l) for 7 h does not affect forearm macro and microcirculatory blood flow or vascular reactivity to noradrenaline in man.