Oxygen and substrate deprivation on isolated rat cardiac myocytes: temporal relationship between electromechanical and biochemical consequences

Abstract

The effects of hypoxia and reoxygenation on action potentials (AP), contractions, and certain biochemical parameters were studied in isolated rat ventricular myocytes in monolayer culture in the presence and absence of glucose. Substrate deprivation alone had no influence on the basal properties. In the presence of glucose, a 4-h hypoxic treatment caused only a moderate decrease in AP amplitude and rate. In substrate-free conditions, hypoxia induced a gradual decline in plateau potential level and in AP duration and rate, followed by rhythm abnormalities and a failure of the electromechanical coupling. Spontaneous AP generation then ceased, and the resting potential decreased with increased duration of hypoxia. These alterations were associated with a decrease in ATP content, an increase in the lactate production, and a leakage of about 50% of the total cellular lactate dehydrogenase (LDH). Cells reoxygenated after 150 min hypoxia recovered near-normal function, while the ATP depletion ceased and the rate of lactate and LDH loss was diminished. Conversely, cells reoxygenated after 4 h hypoxia exhibited a further decrease of the residual resting polarization and no change in the decline of intracellular ATP and in the efflux of cytosolic lactate and LDH. The results of this study indicate that (1) the sequence and the extent of functional alterations are dependent on the duration of hypoxia in the absence of exogenous substrate and (2) ATP depletion and the amount of lactate and LDH released during hypoxia are related to the shift from reversibly to irreversibly damaged cells.

Cross‐influence of membrane polyunsaturated fatty acids and hypoxia‐reoxygenation on α‐ and β‐adrenergic function of rat cardiomyocytes

“…This recovery of contractile properties during reoxygenation was not influenced by the n-6/n-3 PUFA ratio of the CM. The changes in contractile parameters provoked by hypoxiareoxygenation in n-3 and n-6 CM was also similar to those observed in the myocytes maintained in standard culture medium (Ham C CM) (16).…”

“…Cultured neonatal CM display spontaneous and regular beatings in basal salt media, showing that the presence of serum factors or hormonal supplement, such as catecholamines, are not required for the initiation and/or the maintenance of automaticity and contractile function, even during long term experiments. Furthermore, it has been previously determined that cultured rat cardiomyocytes are able to display stable normal function for hours in the presence as well as in the absence of glucose in the bath (16). The culture dish was placed in a heated water-circulation, gas-controlled chamber (17), fitted on the moving stage of an inverted phase contrast microscope.…”

“…In some hypoxia-reoxygenation protocols on reference cells, action potential recording was carried out, together with contraction monitoring, using conventional glass microelectrode as previously described (16).…”

Differential regulation of cardiac heme oxygenase‐1 and vascular endothelial growth factor mRNA expressions by hemin, heavy metals, heat shock and anoxia

“…They can be maintained under anoxic conditions for several hours without impairing spontaneous contractile activity [24]. Fig.…”

β₁-Adrenergic Receptors Maintain Fetal Heart Rate and Survival

“…Hypoxia reduces heart rate in adult and perinatal atrial strips [51][52][53] and cardiomyocytes [54][55][56] , suggesting that a bradycardic response to hypoxia is intrinsic to adult and perinatal cardiac cells. However, the effect of hypoxia has not been assessed in the early fetal heart.…”