Effects of hypoxia on contractility of isolated fetal lamb cerebral arteries |
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Authors: | R D Gilbert W J Pearce S Ashwal L D Longo |
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Affiliation: | Department of Physiology, School of Medicine, Loma Linda University, California. |
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Abstract: | 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. |
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