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Inhibition of cardiolipin biosynthesis in the hypoxic rat heart
Insights
Hypoxia significantly reduces cardiolipin biosynthesis in rat hearts, decreasing phosphatidylglycerol and cardiolipin levels. This inhibition is linked to reduced adenosine-5'-triphosphate and cytidine-5'-triphosphate levels.
Area of Science:
- Biochemistry
- Cardiology
- Cellular Physiology
Background:
- Cardiolipin is a crucial polyglycerophospholipid in cardiac tissue.
- Understanding cardiolipin's role is vital for cardiac health and disease research.
Purpose of the Study:
- To investigate the impact of hypoxia on cardiolipin biosynthesis in isolated rat hearts.
- To identify potential molecular mechanisms underlying changes in cardiolipin synthesis under hypoxic conditions.
Main Methods:
- Isolated rat hearts perfused using the Langendorff technique.
- Pulse-labeling experiments using [1,(3)-3H]glycerol and [32P]Pi under normoxic and hypoxic conditions.
- Quantification of radioactivity incorporated into various lipids and measurement of enzyme activities and metabolite levels.
Main Results:
- Hypoxia significantly reduced radioactivity incorporation into phosphatidylglycerol (88%) and cardiolipin (79%) when labeled with [1,(3)-3H]glycerol.
- Hypoxia also decreased incorporation into CDP-1,2-diacyl-sn-glycerol (61%), phosphatidylglycerol (71%), and cardiolipin (70%) when labeled with [32P]Pi.
- Cardiac adenosine-5 riphosphate and CPT levels were drastically reduced (94% and 92%, respectively) in hypoxic hearts.
Conclusions:
- Hypoxia inhibits cardiolipin biosynthesis in the heart, evidenced by reduced incorporation of precursors.
- The observed inhibition is associated with decreased levels of CDP-1,2-diacyl-sn-glycerol, adenosine-5 riphosphate, and cytidine-5 riphosphate.
- Reduced ATP and CTP levels are postulated as key factors inhibiting cardiac cardiolipin biosynthesis during hypoxia.
Abstract:
Cardiolipin is the principal polyglycerophospholipid in the heart. The effect of hypoxia on cardiolipin biosynthesis was investigated in isolated rat hearts perfused in the Langendorff mode. Hearts were pulsed-labeled for 60 min with 0.1 mM [1,(3)-3H]glycerol in Krebs Henseleit buffer saturated with either 95% O2/5% CO2 (control) or 95% N2/5% CO2 (hypoxic). Radioactivity incorporated into phosphatidylglycerol and cardiolipin were reduced 88% (P < .05) and 79% (P < .05), respectively, in hypoxic hearts compared to controls. In other experiments, hearts were pulse-labeled for 15 min with 1.4 mM [32P]Pi in Krebs Henseleit buffer saturated with 95% O2/5% CO2 and subsequently perfused for 60 min under control or hypoxic conditions. The radioactivity incorporated into CDP-1,2-diacyl-sn-glycerol, phosphatidylglycerol, and cardiolipin were reduced 61% (P < .05), 71% (P < .05), and 70% (P < .05), respectively, in the hypoxic hearts compared to controls, indicating a decreased formation of CDP-1,2-diacyl-sn-glycerol in the hypoxic heart. The activities of the enzymes involved in cardiolipin biosynthesis and the cardiac pool sizes of cardiolipin, phosphatidylglycerol, and CDP-1,2-diacyl-1,2-diacyl-sn-glycerol were unaltered between hypoxic and control hearts. In contrast, cardiac adenosine-5'-triphosphate and CPT levels were decreased 94% (P < .05) and 92% (P < .05), respectively, in hypoxic hearts compared to controls. We postulate that the biosynthesis of the cardiac polyglycerophospholipid cardiolipin may be inhibited by a decreased adenosine-5'-triphosphate and cytidine-5'-triphosphate level in the heart.