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Responses of Systemic Vascular Smooth Muscle to Hypoxia
Author(s) -
Ebeigbe A. B.,
Pickard J. D.,
Jennett Sheila
Publication year - 1980
Publication title -
quarterly journal of experimental physiology and cognate medical sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0033-5541
DOI - 10.1113/expphysiol.1980.sp002517
Subject(s) - contraction (grammar) , hypoxia (environmental) , vasodilation , calcium , hyperoxia , vascular smooth muscle , iodoacetic acid , chemistry , medicine , muscle relaxation , endocrinology , oxygen tension , oxygen , anatomy , anesthesia , biochemistry , smooth muscle , organic chemistry , enzyme
The rapidity and extent of hypoxic relaxation of vascular smooth muscle (VSM) from different systemic vessels is relevant to the study of mechanisms of vasodilatation in different vascular beds. Variations between sites may also assist understanding of the link between oxygen tension and mechanical activity, which has been shown not to be a simple deprivation of aerobic processes. Strips of rat portal vein (RPV), rabbit ear artery (REA) and rabbit common carotid artery (RCC) were studied under isotonic conditions, contracted by 10 –6 noradrenaline (NA). Reduction of Po 2 to less than 3KPa during NA contraction led to relaxation which was rapid and 90% complete in RPV, rapid and 60% in REA: the relaxation began when tissue Po 2 was decreasing and was not lower than 5·5 K Pa. RCC responded slowly and only some strips relaxed. The rapidity and magnitude of relaxation for each type of vessel was comparable to that produced by removal of external calcium. Also for any one type of VSM the response to NA was abolished or diminished to a similar extent by preliminary exposure to hypoxia, or by preliminary removal of calcium. Preliminary hypoxia diminished 50mmol.l –1 K + contractions as much as it diminished NA contractions. Preliminary 1—2 hour exposure to hyperoxia diminished the subsequent relaxant effect of hypoxia. Inhibition of glycolysis (iodoacetic acid) had no effect on normoxic NA contraction or on hypoxic relaxation, but prevented or diminished the subsequent recovery on reoxygenation. Low oxygen tension appears to act in VSM as though it interferes with net influx or utilisation of external calcium.