Messina L M, Gardner A
Jobst Vascular Research Laboratories, Department of Surgery, University of Michigan Medical Center, Ann Arbor 48109.
Microvasc Res. 1992 Nov;44(3):274-85. doi: 10.1016/0026-2862(92)90087-6.
Arterioles may undergo a transient vasoactive response when exposed to light during fluorescent intravital microscopy. We hypothesized that the type and frequency of the vasoactive responses by arterioles to light is calcium dependent. In order to test this hypothesis we quantitated the type and frequency of vasoactive responses by arterioles to light in the presence and absence of calcium within the suffusate bathing the muscle. In addition, we determined whether the presence or absence of calcium also influenced the reactivity of these arterioles to adenosine and norepinephrine. In separate experiments, we determined the effect of increases in suffusate calcium concentration on the resting diameter of arterioles. The concentration of calcium in the suffusate significantly influenced the frequency of light-induced vasoactivity of the arterioles of the tibialis anterior muscle: a normal suffusate calcium concentration of 2 x 10(-3) M was associated with an incidence of light-induced vasoreactivity of 77% but decreased significantly to 58% when calcium was removed from the suffusate. Although the frequency of the vasoactive response to light was different for the two experimental conditions, the type of vasoactive response, predominately vasomotion, was similar. The vasoactive responses of arterioles to adenosine and norepinephrine were similar in the presence and absence of calcium in the suffusate. However, the concentration of calcium in the suffusate did significantly influence resting arteriolar diameters: 2 x 10(-3) M calcium CaCl2 caused a mean decrease in the arteriolar diameter of 11.6 (+/- 3.0)%, 4 x 10(-3) M CaCl2 caused a mean decrease of 41.2 (+/- 12)%, and 8 x 10(-3) M CaCl2 caused a mean decrease of 55.4 (+/- 14.4)%. These results show that the concentration of calcium in the suffusate bathing the tibialis anterior muscle during fluorescent intravital microscopy significantly influences the vasoactive response of arterioles to light. Further investigation of the mechanisms of light-induced effects on microcirculation during fluorescent intravital microscopy will become important as this technique is used more widely in the study of the microcirculation of solid tissues and organs.
在荧光活体显微镜检查过程中，小动脉暴露于光线时可能会发生短暂的血管活性反应。我们假设小动脉对光线的血管活性反应的类型和频率是钙依赖性的。为了验证这一假设，我们在灌注液中存在和不存在钙的情况下，定量了小动脉对光线的血管活性反应的类型和频率。此外，我们还确定了钙的存在与否是否也会影响这些小动脉对腺苷和去甲肾上腺素的反应性。在单独的实验中，我们确定了灌注液钙浓度升高对小动脉静息直径的影响。灌注液中的钙浓度显著影响胫前肌小动脉光诱导血管活性的频率：正常灌注液钙浓度为2×10⁻³ M时，光诱导血管反应性的发生率为77%，但当灌注液中去除钙时，该发生率显著降至58%。尽管两种实验条件下对光线的血管活性反应频率不同，但血管活性反应的类型主要是血管运动，是相似的。灌注液中存在和不存在钙时，小动脉对腺苷和去甲肾上腺素的血管活性反应相似。然而，灌注液中的钙浓度确实显著影响小动脉的静息直径：2×10⁻³ M氯化钙使小动脉直径平均降低11.6（±3.0）%，4×10⁻³ M氯化钙使小动脉直径平均降低41.2（±12）%，8×10⁻³ M氯化钙使小动脉直径平均降低55.4（±14.4）%。这些结果表明，在荧光活体显微镜检查过程中，灌注胫前肌的灌注液中的钙浓度显著影响小动脉对光线的血管活性反应。随着这项技术在实体组织和器官微循环研究中的更广泛应用，进一步研究荧光活体显微镜检查过程中光诱导对微循环影响的机制将变得很重要。
