Pearse D B, Fessler H E, Wagner E M
Division of Pulmonary and Critical Care Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland 21224, USA.
Am J Physiol. 1995 Sep;269(3 Pt 2):H1037-43. doi: 10.1152/ajpheart.1995.269.3.H1037.
The use of microspheres to measure tissue blood flow requires that the microspheres themselves do not alter regional arterial tone. To determine whether microspheres affected bronchial artery resistance, we cannulated and perfused the bronchial artery in anesthetized sheep. In seven sheep, the change in bronchial artery pressure at constant flow was recorded during infusion of 5 doses (1 x 10(5), 2 x 10(5), 5 x 10(5), 1 x 10(6), and 1.5 x 10(6)) of 15-microns microspheres. Microspheres produced a dose-dependent, self-limited decrease in bronchial artery pressure (1.5 x 10(6) microspheres decreased bronchial artery pressure by 36% for 31 min). This was a decrease in bronchial artery resistance, as evidenced by a shift in the slope, but not the intercept, of a pressure-flow curve (n = 4 sheep). Left atrial injection of 1 x 10(7) microspheres decreased bronchial artery resistance by 17% in six sheep with intact bronchial arteries in which flow was measured by ultrasound probe. The adenosine-receptor antagonist 8-phenyltheophylline attenuated the fall in resistance by 79% (n = 4 sheep). Cyclooxygenase inhibition by indomethacin attenuated the response by 37% (n = 4 sheep). These results suggest that microspheres caused the release of adenosine and a vasodilator prostaglandin. Repetitive measurements of bronchial blood flow by microspheres could overestimate true bronchial blood flow if the interval between measurements is < 30 min.
使用微球测量组织血流要求微球本身不会改变局部动脉张力。为了确定微球是否影响支气管动脉阻力，我们在麻醉的绵羊身上插管并灌注支气管动脉。在7只绵羊中，在输注5个剂量（1×10⁵、2×10⁵、5×10⁵、1×10⁶和1.5×10⁶）的15微米微球期间，记录恒定流量下支气管动脉压力的变化。微球使支气管动脉压力呈剂量依赖性、自限性下降（1.5×10⁶个微球使支气管动脉压力在31分钟内下降36%）。这是支气管动脉阻力的下降，压力-流量曲线斜率改变但截距未改变可证明这一点（n = 4只绵羊）。在6只支气管动脉完整且通过超声探头测量血流的绵羊中，经左心房注射1×10⁷个微球使支气管动脉阻力下降17%。腺苷受体拮抗剂8-苯基茶碱使阻力下降减弱79%（n = 4只绵羊）。吲哚美辛抑制环氧化酶使反应减弱37%（n = 4只绵羊）。这些结果表明微球导致了腺苷和一种血管舒张性前列腺素的释放。如果测量间隔<30分钟，通过微球重复测量支气管血流可能会高估真实的支气管血流。
