Gilbert R D, Pearce W J, Ashwal S, Longo L D
Department of Physiology, School of Medicine, Loma Linda University, California.
J Dev Physiol. 1990 Apr;13(4):199-203.
We studied the contractile properties of isolated cerebral arteries in near term fetal lambs, as well as the magnitudes and rates of relaxation during moderate hypoxia. Paired 5-mm segments of basilar, middle cerebral, posterior communicating, and common carotid arteries were suspended in a temperature controlled bath and isometric tension measured during 122 mM K(+)-induced contractions. In one vessel of each pair hypoxia was imposed by switching the bubbling gas from 95% O2 + 5% CO2 to 95% N2 + 5% CO2 4 minutes into a K+ contraction, thus lowering the bath PO2 to approximately 15 Torr. After 15 min exposure to hypoxia the middle cerebral artery had relaxed 61%, the posterior communicating 46%, the basilar 44%, and the common carotid only 18% compared to normoxic controls. All cerebral arteries relaxed relatively rapidly (relaxation rates of 42-45 x 10(-4) s-1), whereas the common carotid relaxed slowly (20 x 10(-4) sec-1). The data indicate that these cerebral arteries play an important role in regulating blood flow responses during hypoxemia in intact fetuses.
我们研究了近足月胎羊离体脑动脉的收缩特性，以及中度缺氧时的舒张幅度和速率。将基底动脉、大脑中动脉、后交通动脉和颈总动脉的5毫米配对节段悬挂于温度可控的浴槽中，在122 mM K⁺诱导收缩期间测量等长张力。在每对血管中的一根血管中，在K⁺收缩4分钟后，将鼓泡气体从95% O₂ + 5% CO₂ 切换为95% N₂ + 5% CO₂ 以造成缺氧，从而将浴槽中的PO₂ 降至约15 Torr。与常氧对照相比，暴露于缺氧15分钟后，大脑中动脉舒张了61%，后交通动脉舒张了46%，基底动脉舒张了44%，而颈总动脉仅舒张了18%。所有脑动脉舒张相对较快（舒张速率为42 - 45×10⁻⁴ s⁻¹），而颈总动脉舒张缓慢（20×10⁻⁴ s⁻¹）。数据表明，这些脑动脉在调节完整胎儿低氧血症期间的血流反应中起重要作用。
