Local vasodilatation with metacholine, but not with nitroprusside, increases forearm glucose uptake

Insulin is known to increase blood flow in parallel to glucose uptake in sk eletal muscle. However, it is not known if an increase in blood flow by its elf is associated with an increase in glucose uptake in the absence of hype rinsulinemia. To investigate further this matter, the effect of increased b lood flow on forearm glucose uptake was studied in the fasting state during intra-arterial infusions of two different vasodilators, metacholine and ni troprusside, in 19 hypertensive subjects. Both metacholine (4 mu g/min) and nitroprusside(10 mu g/min) increased resting forearm blood flow, measured by venous occlusion plethysmography, to a similar degree(180 % and 170 %, r espectively, p<0.0001 for both). However, metacholine infusion increased th e forearm glucose uptake from 2.0+/-0.9 (S.D.) during rest to 5.5+/-3.0 umo l/min/100 mi tissue (p<0.0001), while no significant change in glucose upta ke was seen during nitroprusside infusion (2.3+/-1.4 mu mol/min/100 mi tiss ue). In conclusion, vasodilatation induced by metacholine, but not by nitro prusside, increased glucose uptake in the forearm of hypertensive patients. Thus, an increase in forearm blood flow does not necessarily improve gluco se uptake in the forearm during the fasting state.