RELEASE OF FATTY-ACID-BINDING PROTEIN AND LONG-CHAIN FATTY-ACIDS FROMISOLATED RAT-HEART AFTER ISCHEMIA AND SUBSEQUENT CALCIUM PARADOX

To obtain insight into the relation between the release of heart-type fatty acid-binding protein (H-FABP(c)) and of long-chain fatty acids ( FA) from injured cardiac tissue, rat hearts were Langendorff perfused according to the following scheme: 30 min normoxia, 60 min ischemia, 3 0 min reperfusion, 10 min Ca2+ free perfusion and finally 10 min Ca2repletion. During this protocol right ventricular (Q(rv)) and intersti tial effluent samples (Q(i)) were collected at regular intervals. Duri ng reperfusion a total of 0.8 +/- 0.1 nmol H-FABP, but no FA were dete cted in the effluents. However, during Ca2+ readmission, 45 +/- 4 nmol H-FABP(c) (80-90% of total tissue content) was released with an initi al (first 3 min) simultaneous release of FA (FA/H-FABP, ratio 0.90 +/- 0.07 mol/mol). Thereafter, FA release continued at 10-15 nmol per min mainly in Q(rv) while the rate of H-FABP, release decreased. During C a2+ repletion, tissue FA content raised rapidly from 168 +/- 20 to 191 8 +/- 107 nmol/g dry weight. These findings suggest that after severe cardiac damage initially FA is released bound to H-FABP(c), whereas fu rther FA release occurs in a non-protein bound manner.