Oxygen-dependent regulation of membrane potential and vascular tone of human umbilical vein.

Abstract

We question the hypothesis that vascular tone of human umbilical vein is insensitive to oxygen pressure and minimal already at resting conditions. Isometric tension and intracellular membrane potential of native (n = 7) and endothelium-denuded (n = 7) human umbilical vein strips were recorded simultaneously at oxygen pressure values of 5 to 104 mm Hg. Increasing oxygen pressure from 5 to 104 mm Hg led to graded membrane depolarization from -58.2 +/- 1.3 mV (SEM) to -54.0 +/- 0.7 mV (P <.009) and increased isometric tension from 0.576 +/- 0.016 g to 0.790 +/- 0.032 g (P <.0001). The steepest increase in tension (Delta = 0.063 g) occurred within the physiologic intrauterine oxygen tension range (27-35 mm Hg). Isometric tension at hypoxia (partial oxygen pressure, 5 mm Hg) corresponded to 88% of resting tension. Tension and membrane potential were related linearly (r(2) = 0.99). Disruption of the endothelium reversed the effects of oxygen pressure. Human umbilical vein vascular tone was regulated by oxygen tension and showed a hypoxic vasodilator reserve. Oxygen-dependent effects were related to the membrane potential and required the endothelium.