Reversible and irreversible alterations of lysosomes in ischemic rat-liver. Effects of chlorpromazine

Quantitative changes in acid phosphatase, alkaline phosphatase and 5'-nucleotidase activity in rat liver after experimentally induced cholestasis

Acid phosphatase, alkaline phosphatase and 5'-nucleotidase activities were analyzed cytophotometrically in cryostat sections of rat liver up to 8 weeks after ligation and transsection of the common bile duct. Ligation resulted in cholestasis and induced alterations in both localization and activity of the enzyme investigated. The cellular distribution but not the activity of acid phosphatase changed in liver parenchyma. In control liver, the final reaction product was localized as discrete granules in the bile canalicular region of hepatocytes. The final reaction product was precipitated more diffusely within the cytoplasm after induction of cholestasis, most probably due to increased fragility of lysosomal membranes. In control liver, alkaline phosphatase activity was low and localized in the bile canalicular plasma membranes only. The total parenchymal activity increased threefold after the induction of cholestasis and is considered to be a compensatory mechanism in order to enhance the excretion of bile salts from hepatocytes. 5'-Nucleotidase was present at the bile canalicular and sinusoidal surfaces of plasma membranes of hepatocytes in control liver; total activity in pericentral areas was significantly higher than in periportal areas. Induction of cholestasis resulted in higher total activity and redistribution of the activity over all three surfaces of the plasma membranes, whereas heterogeneity over the different zones of the acinus disappeared. The appearance of the enzyme at lateral plasma membranes is suggested to be related to the formation of new sites for bile salt transport out of the hepatocytes. With respect to all three enzymes studied, alterations of liver parenchymal cells due to a disturbed bile transport were already established during the first week of cholestasis.

Changes in acid phosphatase activity in rat liver after ischemia

The effect of ischemia on the stability, i.e. the permeability of the lysosomal membrane of rat liver has been studied using quantitative histochemical analysis of acid phosphatase activity. Ischemia in vitro was performed for 0-240 min at 37 degrees C and ischemia in vivo for 60 min was followed by 1, 5, 24 and 48 h of reperfusion. Acid phosphatase activity was demonstrated in cryostat sections using naphthol AS-BI phosphoric acid as substrate and polyvinyl alcohol was added to the incubation medium to counteract diffusion phenomena. Ischemia in vitro up to 240 min did not affect the localization nor the total activity of acid phosphatase activity. After 60-min ischemia in vivo followed by 1-h reperfusion distinct areas showed decreased acid phosphatase activity. A further decrease in activity was observed after 5 h reperfusion. Final reaction product generated by acid phosphatase activity was rather diffusely distributed in border zones between normal and damaged tissue after 24 and 48 h of reperfusion following 60 min ischemia in vivo. It is concluded that not ischemia itself but rather reperfusion affects the stability of the lysosomal membrane due to the occurrence of oxygen-derived free radicals and/or imbalanced Ca2+ concentration. Restoration of the blood flow causes leakage of acid phosphatase from the lysosomes into the cytoplasm of liver parenchymal cells and from there to the blood.

Effects of chlorpromazine and methylprednisolone on perfusion preservation of rabbit livers

The isolated perfused rabbit liver was used to determine how continuous hypothermic perfusion affected liver function. Rabbit livers were perfused for 0, 24, 48, and 72 hr at 5 degrees C with the UW perfusate containing hydroxyethyl starch (5 g%) dissolved in a solution containing gluconate (80 mM), adenosine (5 mM), glutathione (3 mM), phosphate (25 mM), and additives as described previously, and they were used successfully for kidney preservation. At the end of preservation the livers were perfused in an isolated circuit with a Krebs-Henseleit solution with addition of 4 g% bovine serum albumin and 10 mM glucose at 38 degrees C for 120 min. Bile was collected from the cannulated common duct. Biliary excretions of indocyanine green and liver enzymes lactate dehydrogenase, aspartate aminotransferase, and alanine aminotransferase, were determined both in the cold perfusate and the normothermic perfusate. Livers were also studied after pretreatment of the donor with chlorpromazine (CPZ) and/or methylprednisolone (MP). Bile production (ml/120 min, 100 g liver) upon reperfusion produced the most interesting data and decreased from a control value of 10.3 +/- 2.6 to 9.3 +/- 1.0 (24 hr), 5.3 +/- 0.7 (48 hr), and 4.1 +/- 1.5 (72 hr). Enzyme release was not predictive of the degree of preservation-induced damage. Pretreatment of rabbits with a combination of CPZ/MP improved bile flow at 48 and 72 hr (8.3 +/- 3.0 and 7.0 +/- 1.3, P less than 0.05). Pretreatment with either drug alone also improved function after 72 hr of preservation (7.1 +/- 1.8, CPZ; 8.2 +/- 3.5, MP).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of drug treatment on liver-slice function following 72-hour hypothermic perfusion

The viability of hypothermically perfused dog liver was evaluated with a tissue-slice technique. After being preserved for 72 hr, slices of liver were incubated at 30 degrees C for as long as 2 hr; then water content, K+/Na+ ratio, and ATP concentration were measured. Dog livers were assigned to the following experimental groups: Group 1 (no preservation; control); Group 2 (livers preserved for 72 hr); Group 3 (donor animals pretreated with 3.5 mg/kg of chlorpromazine (CPZ) and 20 mg/kg of methylprednisolone (MP), and livers preserved for 72 hr); Group 4 (livers pretreated with 2-deoxycoformycin (2-DOC), 50 mg/liter, and preserved for 72 hr); and Group 5 (combination of Group 3 and Group 4 treatments). Livers in Groups 2, 3, and 4 lost K+ during preservation, and the mean K+/Na+ ratio significantly decreased from a control value of 4.2 +/- 0.4 to 1.5-1.9 (P less than 0.05). Group 5 livers did not lose K+; mean K+/Na+ ratio was 3.9 +/- 0.5. Fresh livers (no preservation) rapidly reaccumulated K+ when the tissue slices were incubated for 2 hr at 30 degrees C; mean K+/Na+ ratio was 3.7 +/- 0.5. Tissue slices from Group 2 livers (72 hr preservation), and livers pretreated with CPZ-MP (Group 3) or pretreated with 2-DOC (Group 4) did not significantly reaccumulate K+ at 30 degrees C; mean K+/Na+ ratio was 1.7-2.1. Only slices prepared from liver pretreated with both CPZ-MP and 2-DOC reaccumulated K+; mean K+/Na+ ratio was 4.6 +/- 1.2.(ABSTRACT TRUNCATED AT 250 WORDS)

Phospholipid alterations and membrane injury during myocardial ischemia

Several independent studies have demonstrated that there is a degradation of membrane phospholipids during myocardial ischemia. At present, most of the data support the initial activation of a phospholipase A pathway of phospholipid degradation. The extent of total phospholipid degradation is in the nanomole per gram wet weight quantity, as opposed to ischemic liver, in which the extent of phospholipid depletion approaches the micromole per gram wet weight level. However, in vitro studies suggest that calcium permeability properties and other myocardial cell membrane functions are sensitive to nanomole levels of phospholipid degradation. Clearly, further work is necessary in intact cell and heart preparations to correlate the degradation of phospholipid with the development of irreversible membrane injury during ATP depletion and hypoxia.

Accumulation of unesterified arachidonic acid in ischemic canine myocardium. Relationship to a phosphatidylcholine deacylation-reacylation cycle and the depletion of membrane phospholipids

Studies in ischemic canine left ventricle have shown that the depletion of membrane phospholipids is a critical event in the development of a sarcolemmal calcium permeability defect and associated irreversible myocyte injury. The mechanism of phospholipid loss is unclear, but may be due to the activation of endogenous phospholipases. Since arachidonic acid is a fatty acid found almost entirely in phospholipid, increases in arachidonate provide evidence for increased phospholipase activity. The present study was designed to examine the temporal relationship of the accumulation of free arachidonate with the onset of phospholipid depletion during fixed ligation of the left anterior descending coronary artery in canine myocardium. The following results were demonstrated in ischemic canine myocardium: (1) the accumulation of unesterified arachidonate is minimal during 10-30 minutes of ischemia, but is significantly increased after prolonging the duration of ischemia to 1-3 hours; (2) significant increases in arachidonate precede the development of a significant decrease in total phospholipid content; (3) the decrease in the arachidonate content of phosphatidylcholine is accompanied by similar decreases in all of the fatty acyl moieties; (4) the arachidonate content of lysophosphatidylcholine and diacylglycerol are unchanged during myocardial ischemia; (5) there is evidence of a deacylation-reacylation cycle in phosphatidylcholine prior to the accumulation of free arachidonate; (6) the fatty acyl specificity of the lysophosphatidylcholine acyltransferase corresponds to the pattern of fatty acyl remodeling of phosphatidylcholine during early myocardial ischemia. These data suggest that the accumulation of arachidonate may be a more sensitive measure of phospholipid degradation than the decrease in total phospholipid content in ischemic canine myocardium. It is postulated that the defective reacylation of arachidonate into phosphatidylcholine may contribute to the net loss of membrane phospholipid during myocardial ischemia.