[Effects of continuous laser on arterial vasomotoricity in vitro]

The effects of a continuous-wave argon laser irradiation on arterial vasomotricity were studied isometrically on 19 aortic segments obtained from rabbits. The segments had a resting tension of 1 g and were suspended in a perfusion chamber filled with a Krebs-bicarbonate buffer solution at 37 degrees C gassed with 95 p. 100 O2 and 5 p. 100 CO2. Irradiation was performed with an argon laser emitting principally at 488-514 nm, via a flexible optical fibre 200 microns in diameter. The tension of each specimen, measured with a strain gauge, was recorded at the same time as the arterial wall temperature, measured by a thermistor probe. The integrity of the endothelium was checked by scanning electron microscopy and acetylcholine test. The endothelium of 5 specimens was deliberately abrased, and this was checked by the same methods. Laser irradiations of more than 1 watt regularly (n = 34) induced a contraction the kinetics of which were parallel to those of the arterial wall heating and usually reversible after the end of irradiation. With irradiations of less than 0.1 watt, the parietal temperature never rose by more than 5 degrees C, and the vasomotor response always (n = 41) was a relaxation which was reversible after irradiation. At intermediate levels of power, the vasomotor response was biphasic and of low amplitude (n = 100). At all levels, similar responses were given by specimens whose endothelium had been removed. Thus, at the powers used for angioplasty, irradiation of the arterial wall by continuous-wave argon laser induces and intense vasoconstriction which is independent of the endothelium.(ABSTRACT TRUNCATED AT 250 WORDS)