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  • Title: A novel approach to the study of human microcirculation: Reactivity to locally applied angiotensin II in the conjunctival microvascular bed.
    Author: Houben AJ, Burgwinkel JP, de Leeuw PW.
    Journal: J Hypertens; 2006 Nov; 24(11):2225-30. PubMed ID: 17053544.
    Abstract:
    OBJECTIVE: To develop a state-of-the-art, computer-assisted intravital microscopy protocol to evaluate directly the effects of topically applied drugs on conjunctival arteriolar and venular diameters. METHODS: Fifty-one normotensive volunteers were studied. Video-recordings of the bulbar conjunctival microcirculation were made before and following eye drops containing angiotensin II (AngII) (0.001% w/w, or 0.01%) or phenylephrine (0.25%). The computer-assisted analyses of arteriolar and venular diameters were performed off-line. In different protocols the microvascular reactivity to the different eye drops were compared. RESULTS: AngII (0.01%) eye drops, but not AngII (0.001%), induced significant constriction in both arterioles (median, 19%) and venules (13%). Phenylephrine eye drops (pharmacological control) induced similar arteriolar (18%) and venular (12%) constrictions. Repeated AngII challenges with a 30-min interval revealed reproducible vasoconstriction responses (median arteriolar constriction, 11 and 17%, respectively; NS). The vasoconstriction responses following AngII challenges on two consecutive days revealed reproducible responses (median arteriolar constriction, 13 and 11%, respectively; NS). CONCLUSIONS: The present results demonstrate that the proposed model for noninvasive intravital video-microscopy of the conjunctival microcirculation is sensitive for measuring direct arteriolar and venular reactivity following topically applied drugs. We consider this model a valuable tool for sophisticated research on in-vivo microvascular reactivity in humans.
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