Effects of graded hypoxia on contraction of cultured chick embryo ventricular cells

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Abstract
The quantitative relationship between decreased O2 tension (PO2) and degree of depression of contractile function is difficult to define in intact myocardial tissues because of uncertainty in estimation of diffusion limitations. Effects of hypoxia on contractility in a system with minimal series diffusion barriers, consisting of single cells within spontaneously contracting monolayers cultured from 10 day old chick embryo ventricles was studied. Reversible decreases in amplitude and velocity of cell wall motion occurred over a 3-4 min period when perfusate PO2 was < 12 mm Hg and maximum depression to .apprx. 30% of control levels occurred at PO2 values < 4 mm Hg. On reoxygenation, recovery of amplitude and velocity of contraction occurred in < 15 s. Inhibition of glycolysis with 0.1 mM iodoacetate decreased contraction amplitude and a significantly slowed beating rate during hypoxia. The critical PO2 at which contractile function became impaired was increased to .apprx. 16 mm Hg. High-energy phosphates derived from anaerobic glycolysis might support a reduced level of contractility during brief periods of hypoxia in cultured heart cells.

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