We previously observed that vascular rings of rat thoracic aorta irradiated with Argon ion laser (λ=514.5nm) reproduciblly showed either contraction or relaxation. To study the mechanism of the contraction, vascular contraction induced by laser irradiation in Krebs buffer was compared with that in the following solutions: 1)Ca-free 10mM-EGTA containing buffer; 2)Krebs buffer with 5mM procaine; 3)Ca-free EGTA containing buffer with 5mM procaine. Vascular rings were suspended isometrically with 2.0g tension and irradiated via optical fiber(φ=200μm) into the vascular ring. In each solution, the irradiated vascular ring contracted with same character. These results suggest that vascular contraction due to laser irradiation is independent of the extracellular Ca2+ influx and/or Ca2+ release from sarcoplasmic reticulum.
