The Effects of Nitroglycerin and Amyl Nitrite on Arteriolar and Venous Tone in the Human Forearm

The effects of sublingual nitroglycerin and inhaled amyl nitrite on the arteriolar and venous beds of the forearm were studied in 11 normal subjects. Forearm blood flow was measured with a strain-gauge plethysmograph, and venous tone was determined both by an acute occlusion technic, and by several equilibration technics. Nitroglycerin reduced systemic arterial pressure, elevated forearm blood flow, lowered forearm vascular resistance and decreased venous tone. Amyl nitrite diminished arterial pressure, elevated forearm blood flow, markedly decreased forearm vascular resistance, but in contrast to nitroglycerin augmented venous tone strikingly. This venoconstriction was abolished or diminished when adrenergic activity was impeded by administration of either guanethidine or reserpine.