[Mechanism of changes in the calcium permeability of the sarcolemma of vascular smooth muscle cells during hypoxia].

In isolated preparations of smooth muscle of the rat portal vein, removal of Ca2+ from perfusate or addition of Ca2+--antagonists as well as hypoxia entailed inhibition of vascular smooth muscle contractile activity. Uptake of 45Ca by vascular smooth muscle cells was diminished in hypoxia. Liposomes filled with Ca2+ or Cr but not ATP prevented the hypoxic relaxation of vascular smooth muscle. One of the main reasons of the decrease of vascular smooth muscle contractility in hypoxia seems to be the disturbance of calcium channel phosphorylation and the decrease of sarcolemma calcium permeability.