Effect of hypoxia on calcium exchange in neonatal mammalian myocardium

Publisher Website
Google Scholar
Abstract
The effect of myocardial hypoxia and reoxygenation of Ca exchange was studied in isolated, arterially perfused neonatal rabbit septum. Studies were performed at a flow rate of 2.0-2.5 ml .cntdot. g-1 .cntdot. min-1 at 27.degree. C and a frequency of 30 or 90 beats/min. The extracellular space was determined using 58Co-labeled EDTA as a marker. Gamma-emitting isotopes, 47Ca and 58Co, were used to determine tissue uptake of these ions. 45Ca and 42K were used in the measurement of Ca and K efflux, respectively. The rate of 47Ca uptake was unchanged during hypoxia and increased significantly during reoxygenation. Ca efflux, determined from effluent analysis, was not altered during hypoxia or reoxygenation. Ca influx increased significantly with increased age and with heart rate. Glucose-free perfusate increased Ca influx; perfusate containing 20 mM glucose prevented the increase in Ca influx and improved function. Hypoxia increased K efflux, but this effect was reversed during reoxygenation. Apparently, hypoxia increases the permeability of the sarcolemma to K, but not to Ca. Reoxygenation increases sarcolemmal permeability to Ca but not to K, and this effect is dependent on the myocardial energetic state. Apparently, hypoxia effects the lipid bilayer and reoxygenation after hypoxia affects the surface membrane.