In vivo incorporation of 3H-glycerol and 14C-palmitate into lipids of subcellular fractions of the myocardium hypertrophied during experimental hypoxia.

Incorporation of labelled precursors into neutral lipids and phospholipids of hypertrophied guinea-pig cardiac ventricles during normobaric hypoxia (breathing gas mixture of N2: O2, 9: 91%) was studied. The lipids of the heart were isotopically labelled in vivo with [1-14C] palmitate and [2-3H] glycerol, and, after a period of 2 hours, the incorporation of the two injected precursors into mitochondrial and microsomal fractions was determined. Eighty hours after the onset of the hypoxic treatment, the specific activities of isolated lipids showed a more elevated incorporation into lipid classes of hypoxic right and left ventricles with respect to that of the control. For both precursors, the percent increase of incorporation into microsomal and mitochondrial neutral lipids was higher than into phospholipids. In the microsomal fraction the increase of 14C-radioactivity incorporation was more pronounced than 3H-incorporation. 3H/14C incorporation ratio appeared decreased in hypoxic ventricles. The data in this experiment suggest that the net increase of 3H-glycerol and 14C-palmitate incorporation into myocardial lipid classes was a compensatory response of the heart to the hypoxic stimulus.