[Effect of nitrates on arterial blood vessels exemplified by the radial artery].

Nitrates act, in part, by causing systemic venodilation. In addition, nitrates lead to dilation of arterial conductance vessels. The maximal dilation capacity and threshold of arterial conductance vessels have so far not been examined thoroughly. Therefore, we tested the radial artery diameter before and after i.v. nitroglycerin infusions at increasing dosages (0.015, 0.05, 0.15, 0.5, and 1.5 micrograms/kg/min), 7 min each dose in 28 patients with suspected coronary artery disease (mean age +/- SEM 58 +/- 2 years) using a high resolution ultrasound devise. The low doses of 0.05 and 0.15 microgram/kg/min, equal to dose of 2.5 mg/12 hours and 7.5 mg/12 hours in a patient with 70 kg, led to substantial increases in the cross sectional luminal area of the radial artery of 14.8 +/- 1.5% and 29.3 +/- 2.2%*, (*p < 0.05 vs baseline). The maximal increase (dilatory capacity) was 53.8 +/- 3.8% (mean diameter at baseline: 2.7 +/- 0.1 mm, maximal 3.4 +/- 0.1 mm, p < 0.001). The nitrate sensitivity of the radial artery was estimated by calculation of the ED50, the dose that caused half-maximal dilation of the radial artery. The ED50 of the radial artery was 0.13 +/- 0.003 microgram/kg/min. In conclusion, nitroglycerin leads to a dose dependent dilatation of peripheral conductance vessels. Low doses of 0.05 and 0.15 microgram/kg/min lead to significant arterial dilation. The maximal dilatory capacity of the radial artery is 53.8 +/- 3.5%.