In the present study we investigated the concentrations of cardiac cytoplasmic fatty acid-binding protein (H-FABPc) in various regions of the left and right ventricles of both Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). To this end, the ventricles of six WKY and six SHR hearts were cut in three slices, which were further dissected in one right ventricular piece and ten left ventricular pieces (five inner layer and five outer layer pieces). After homogenisation. H-FABPc was assessed using an Enzyme Linked Immuno Sorbent Assay (ELISA) of the sandwich type. It was found that, when expressed per gram wet tissue, the overall concentration of H-FABPc tended to be lower in SHR than in WKY hearts (874 +/- 53 micrograms/g and 955 +/- 51 micrograms/g, respectively; 0.1 less than P less than 0.2, means +/- S.E.M. for n = 6 animals in each group). However, due to a 30-35% higher ventricular heart mass in SHR than in WKY, the total H-FABPc content per heart turned out to be about 20% higher in SHR than in WKY rats. No concentration differences could be detected between right and left ventricles in WKY and SHR but a marked difference between the outer layer and the inner layer of the left ventricular wall was monitored in both groups. In general, the concentration in the outer layer was 5-15% higher than in the corresponding inner layer. These differences reached the level of significance (P less than 0.05) in regions close to the basis of the heart.