Effects of hypoxia on passive electrical properties of canine ventricular muscle

The effect of hypoxia, either in the presence or in the absence of glucose, on the passive electrical properties of canine ventricular muscle fibers was examined, employing a single sucrose gap method. The significant changes after 30 min of hypoxia (PO2 = 35-45 mm Hg) were an increase in the specific internal longitudinal resistance (Ri) and a decrease in the space constant (lambda). The values during the control (PO2 greater than 450 mm Hg) were 198 +/- 77 omega cm for Ri and 0.81 +/- 0.15 mm for lambda, and they changed to 245 +/- 90 omega cm and 0.70 +/- 0.10 mm, respectively, after 30 min of hypoxia. Hypoxia decreased the specific membrane resistance (Rm), but the changes were not statistically significant. The membrane time constant (tau m) and capacity (Cm) were not affected significantly. The absence of glucose during hypoxia was found to cause more profound changes than hypoxia alone in the passive electrical properties, especially Ri and lambda, suggesting that glucose might counteract the effects of hypoxia on these parameters of ventricular muscles.