Abstract
Human in vivo sublingual microvessels new observed directly after administrating nitroglycerin (Glyceryl trinitrate; GTN) by our novel needle-type CCD intravital microscope (magnification 200×). Subjects were all healthy and non-smoker volunteers. Hemodynamics were monitored continuously using a non-invasive automatic tonometer at sitting position. After mental and physical relaxation, the control images were taken by making an access of the needle lens probe (diameter; 4mm) onto sublingual microvessels. Then microvascular diameter changes after GTN were monitored for 5min. The images were stored on the videotape with hemodynamic data was transferred to a computer, and the diameter changes of the microvessels were analyzed at end diastole. The microvessels were divided into two groups (arteriole or venule<100μm and small artery or vein≥100μm), because of their possible different responses to nitroglycerin. The sublingual microvessels could be observed clearly in all subjects. The diameter of venules dilated gradually after GTN and its dilatory responses were continued. Small veins dilated, but they exhibited smaller responses than venules. Their maximum dilation was 18±3% and 8±2%, respectively (p<0.05, vs. control). Arterioles showed dilatory responses as seen in venules. Arteriolar and small arteries maximum diameter dilation was 25±4% and 8±4%, respectively (p<0.05, vs. control). In conclusion, the sublingual microvessels were clearly visualized non-invasively by our needle-type CCD intravital microscope. The degree of vasodilation to GTN was higher in venules and arterioles (<100μm) than small veins and arteries (≥100μm) in human. Those vascular changes may be important for reduction both preload and afterload, relieving anginal attack.
