Phospholipases of the myocardium

Oxygen free radical-induced injury in isolated rat hearts: effects of ibuprofen and BW 755c

Inhibitors of the arachidonic acid metabolism (AA) as well as scavengers of oxygen free radicals (OFR) have been shown to reduce myocardial infarct size. We investigated the effects of two inhibitors of AA metabolism on the cardiac effects of OFR. Isolated rat hearts were retrogradely perfused for 10 min with buffer containing hypoxanthine (HX, 1 mmol l-1) and xanthine oxidase (XOD: 24 U l-1) alone (n = 11), or with the addition of ibuprofen (IBU) (n = 6) (a cyclooxygenase inhibitor) or BW 755C (n = 6) (a dual inhibitor of cyclo-oxygenase and lipoxygenase). The hearts were observed for 30 min thereafter (total observation time 40 min). Left-ventricular pressures were measured by a balloon in the left ventricle. HX + XOD significantly reduced left-ventricular developed pressure (LVDP) and coronary flow (CF), but not heart rate. The reduction of LVDP and CF was not significantly ameliorated by the addition of IBU (7.6 x 10(-4) mol l-1) or BW 755C (2 x 10(-3) mmol l-1). OFR increased left-ventricular end-diastolic pressure (LVEDP) from (mean +/- SEM) 0 to 22 +/- 4 mmHg (10 min) and 30 +/- 5 mmHg (40 min). Upon addition of IBU, LVEDP increased from 0 to 24 +/- 8 mmHg and 17 +/- 6 mmHg at 10 and 40 min respectively. The addition of BW 755C almost completely inhibited the increase in LVEDP (1 +/- 1 mmHg and 3 +/- 3 mmHg at 10 min and 40 min). In conclusion, except for inhibition of OFR-induced diastolic dysfunction by BW 755C, neither BW 755C nor IBU appear to inhibit cardiac injury induced by OFR.

Isolation and characterization of parenchymal cells from experimentally induced macronodular rat liver cirrhosis

Hepatocytes were isolated from thioacetamide (TAA)-induced macronodular cirrhotic rat livers by a collagenase perfusion method. In the content of cellular metabolites, fatty acid uptake and lipid secretion there were no substantial differences compared with cells isolated from micronodular cirrhosis described previously. In contrast to isolated hepatocytes from normal livers those from macronodular cirrhosis had a lowered cellular content of triglycerides, phospholipids and cholesterol but not of cholesterol esters and free fatty acids. In macronodular cirrhosis hepatocytes of hypertrophic type, rich in cell organelles, can be distinguished ultrastructurally from those with signs of atrophy and degeneration. Immediately after isolation many hepatocytes isolated from macronodular cirrhosis showed plasma membrane blebbing. Whereas the blebbing was without recognizable effects on the fine structure of the isolated hepatocytes of the hypertrophic type, in the more atrophic ones some mitochondria were swollen. In addition, morphological analysis of the crude and purified suspensions revealed a partial selection of the hypertrophic cells during the isolation procedure, presumably due to a more labile state of those cells which showed signs of atrophy and degeneration. When stabilized in the suspension medium, however, the hepatocytes maintained complex metabolic functions for at least 2 h. Thus, the method described allows the isolation of parenchymal cells from TAA-induced macronodular cirrhotic livers for studying ultrastructural and biochemical alterations in hyperregenerative experimental liver cirrhosis.