May 1, 1977

Mechanical, electrical, and biochemical effects of hypoxia and substrate removal on spontaneously active vascular smooth muscle

Acta Physiologica Scandinavica
P HellstrandK Norberg

Abstract

Effects of hypoxia and glucose-free solution on the isolated rat portal vein were studied. Decrease of extracellular PO2 below 50 mm Hg caused graded inhibition of spontaneous mechanical activity; below 7 mm Hg, inhibition was complete in most preparations. Contracture force of depolarized portal vein was less sensitive to decreases in PO2. Responses to noradrenaline at all concentrations were markedly depressed at extreme hypoxia. Sucrose-gap experiments showed that hypoxia reduced the spontaneous electrical spike discharge. Mean tissue contents of PCr, ATP and glycogen (expressed as glucose) were 3.02, 2.47 and 5.07 micromol/g cell wt. in spontaneously active control muscles and 1.07, 1.65 and 1.83 after 20 min anoxia. Physiological variations in PO2 may influence myogenic activity of vascular smooth muscle largely through an action at the membrane level and this mechanism may participate in local blood flow control. Caculations indicated that the graded response to hypoxia in the present in vitro experiments was not due to diffusion limitation. Spontaneous mechanical activity was relatively well maintained even after prolonged exposure to glucose-free solution, whereas the responses to K+ and noradrenaline were markedly supp...Continue Reading

Mentioned in this Paper

Muscle, Smooth, Vascular
Neoton
Contracture
Extracellular
Depressed - Symptom
Entire Portal Vein
Amino Acids, I.V. solution additive
Resting Potentials
Entire Trunk of Portal Vein
Portal Vein Structure

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