Phospholipid composition of immature rat myocardium exposed to chronic hypoxia and the effect of normoxic recovery
Abstract
Four-day-old male Wistar rats were exposed to intermittent high-altitude (IHA) hypoxia of 7000 m simulated in a hypobaric chamber (8 h/day, 5 days/week, 25 exposures). The concentration of individual phospholipids (PL) and fatty acid (FA) composition of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and diphosphatidylglycerol (DPG) were determined in right (RV) and left (LV) ventricles of rats adapted to chronic hypoxia (40-day-old), rats after 30 days of recovery from hypoxic to normoxic conditions (70-day-old) and both age-matched controls.
The adaptation to IHA hypoxia decreased the concentration of DPG in LV (by 10%) in comparison with normoxic control. In hypoxic group the proportion of linoleic acid (18: 2n-6) decreased; on the contrary, the proportion of arachidonic (20: 4n-6), docosapentaenoic (22: 5n-3) and docosahexaenoic (22: 6n-3) acids increased in PC and PE of both RV and LV.
As to DPG, IHA hypoxia caused a significant decrease in the n-6/n-3 ratio due to the increase in the 22: 6n-3 proportion in RV. Thirty-day-long recovery from hypoxic to normoxic conditions led to complete regression of the hypoxic effect on FA composition in all PL.
No difference in FA composition of PL was observed between RV and LV in any experimental group. Numerous dietary studies with fish oil supplements confirmed cardioprotective effect of n-3 polyunsaturated FA.
We suppose that their increased content in heart-membrane PL observed in this study independently on a diet might contribute to higher tolerance of chronically hypoxic myocardium to ischemic injury.