Abstract
The effects of hypoxic (pO2 < 40 mmHg)/glucose-free media on resting sarcolemmal calcium (Ca) permeability and cellular Ca content in the neonatal (2-4 day old) rat atrium were studied using isotopic Ca (45Ca). Experiments (each > 12 atria) were completed at 37°C. The atria were then placed in 4°C Tyrode's solution containing 6.8 mM Ca/5 mM EGTA for 45 min to displace extracellular 45Ca. Ca uptake (earcolemma 1 Ca permeability) was increased significantly from 45.3±16.5 (SD) to 85.8±28.5 μmol/kg following 2 hr exposure to hypoxic/glucose-free solution (p < 0.001) and from 37.0±8.2 to 124.9±16.2 μmol/kg (p < 0.001) following 3 hr exposure. After 2 hr, Ca content was increased from 0.69±0.25 to 1.00±0.17 mmol/kg and after 3 hr from 0.84±0.24 to 2.70±0.62 mmol/kg (p < 0.001 from both). Cooling tissues to 27 C during the Ca uptake period (1 min) reduced control Ca uptake from 32.5±14.5 to 20.0±5.5 μmol/kg, a 38% decrease (p < 0.01), and the uptake measured in hypoxic/glucose-free tissues (3 hr) from 100.4 ± 18.7 to 75.6 ± 14.2 μmol/kg, a 25% decrease (p<0.001). At 7°C, Ca uptake under both conditions was reduced by ∼80%. Control and 3 hr hypoxic/glucose-free Ca uptakes were not affected by diltiazem (5×10-6 M). In conclusion, hypoxic/ glucose-free conditions in the neonatal rat atrium increase sarcolemmal Ca permeability and cellular Ca content. We hypothesize that the increased permeability is not the result of “breaks” in the sarcolemma (temperature sensitivity of the increased Ca uptake) nor Ca flux via diltiazem-sensitive Ca channels, but may result indirectly from the rise in intracellular sodium during these conditions.
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Lodge, N., Gelband, H. THE EFFECTS OF ISCHEMIC CONDITIONS (HYPOXIA AND GLUCOSE DEPRIVATION) ON CALCIUM REGULATION IN THE NEONATAL RAT MYOCARDIUM. Pediatr Res 21 (Suppl 4), 191 (1987). https://doi.org/10.1203/00006450-198704010-00151
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DOI: https://doi.org/10.1203/00006450-198704010-00151