Analysis of erythrocyte and platelet membrane proteins in various forms of beta-thalassemia.

Major membrane proteins have been quantitatively analyzed in erythrocytes and platelets from patients with homozygous (splenectomized and non-splenectomized) and heterozygous forms of beta-thalassemia depending on severity of clinical manifestation of this disease. Quantitative analysis of erythrocyte membrane proteins revealed increase in alpha- and beta-spectrin. (In non-splenectomized patients with homozygous beta-thalassemia the amount of this protein was lower than in corresponding controls.) Besides spectrin, the increase of 2.1-2.3 fractions of ankyrin, and the decrease of band 3 protein (anion-transport protein), 4.1, palladin, and glyceraldehyde-3-phosphate dehydrogenase were also found. Analysis of major platelet membrane proteins revealed significant increase in gelsolin. This increase was found in all forms of beta-thalassemia irrespective of gender. Significant changes in platelet membrane protein fractions were found in patients (especially non-splenectomized) with homozygous beta-thalassemia. These included significant decrease in myosin, profilin, and gamma-actin and increase in actin-binding protein in both male and female patients. The content of other protein fractions (alpha-actinin, tubulin, tropomyosin) remained unchanged. Changes in protein fractions of erythrocytes and platelets correlated with severity of clinical manifestation of the disease.

Protection of hearts from reperfusion injury by propofol is associated with inhibition of the mitochondrial permeability transition.

OBJECTIVE: Diminishing oxidative stress may protect the heart against ischaemia-reperfusion injury by preventing opening of the mitochondrial permeability transition (MPT) pore. The general anaesthetic agent propofol, a free radical scavenger, has been investigated for its effect on the MPT and its cardioprotective action following global and cardioplegic ischaemic arrest. METHOD: Isolated perfused Wistar rat hearts were subjected to either warm global ischaemia (Langendorff) or cold St. Thomas' cardioplegia (working heart mode) in the presence or absence of propofol. MPT pore opening was determined using [3H]-2-deoxyglucose-6-phosphate ([3H]-DOG-6P) entrapment. The respiratory function of isolated mitochondria was also determined for evidence of oxidative stress. RESULTS: Propofol (2 micrograms/ml) significantly improved the functional recovery of Langendorff hearts on reperfusion (left ventricular developed pressure from 28.4 +/- 6.2 to 53.3 +/- 7.3 mmHg and left ventricular end diastolic pressure from 52.9 +/- 4.3 to 37.5 +/- 3.9 mmHg). Recovery was also improved in propofol (4 micrograms/ml) treated working hearts following cold cardioplegic arrest. External cardiac work on reperfusion improved from 0.42 +/- 0.05 to 0.60 +/- 0.03 J/s, representing 45-64% of baseline values, when compared to controls (P < 0.05). Propofol inhibited MPT pore opening during reperfusion, [3H]-DOG-6P entrapment being 16.7 vs. 22.5 ratio units in controls (P < 0.05). Mitochondria isolated from non-ischaemic, propofol-treated hearts exhibited increased respiratory chain activity and were less sensitive to calcium-induced MPT pore opening. CONCLUSION: Propofol confers significant protection against global normothermic ischaemia and during cold cardioplegic arrest. This effect is associated with less opening of mitochondrial MPT pores, probably as a result of diminished oxidative stress. Propofol may be a useful adjunct to cardioplegic solutions in heart surgery.

Quantitative evaluation of relationship between cardiac energy metabolism and post-ischemic recovery of contractile function.

Quantitative Evaluation of Relationship between Cardiac Energy Metabolism and Post-ischemic Recovery of Contractile Function. Mechanisms of ischemic damage were studied by defining the relationships between post-ischemic work recovery and tissue ATP levels in isolated rat hearts as well as mitochondrial respiration rates in skinned myofibrils. Pre-ischemic levels of ATP were reduced by 2-deoxyglucose treatment and assessed using 31P-NMR. A 70% fall of ATP was not associated with decreased functional recovery. Mitochondrial respiration was assessed without mitochondrial isolation in skinned cardiac fibers in physiological salt solution using a novel method developed by Veksler et al. Maximal rates of mitochondrial respiration were not changed after 35 min of normothermic ischemia using St. Thomas's Hospital cardioplegic solution followed by 30 min of aerobic reperfusion. Only a reversible increase in the rate of basal respiration and a decrease in creatine-stimulated oxygen uptake were observed. Thus, mitochondrial oxidative phosphorylation, as assessed in skinned myofibrils, was tolerant to an ischemic period which induced permanent depression of contractile function along with alterations in metabolite distribution. As a result, tissue level of ATP and rates of mitochondrial respiration provided an estimate of ischemic damage only in cases where damage reached a very severe extent.

Protection of ischemic myocardium by exogenous phosphocreatine. I. Morphologic and phosphorus 31-nuclear magnetic resonance studies.

A phosphorus 31-nuclear magnetic resonance method was used to study the effect of exogenous phosphocreatine on the isolated perfused rat heart. The hearts were chemically arrested by St. Thomas' Hospital solution and made totally ischemic for 35 minutes at 37 degrees C. In the presence of phosphocreatine, 10 mmol/L, during ischemia, almost complete recovery of heart function and phosphocreatine content and 61% recovery of adenosine triphosphate content were observed after 30 minutes of postischemic reperfusion; in the control experiments without phosphocreatine, contractile function, intracellular phosphocreatine, and adenosine triphosphate contents were restored to 33%, 43%, and 26% of their normal values, respectively. Ultrastructural studies with a lanthanum tracer method showed remarkable protection of sarcolemma against ischemic injury by exogenous phosphocreatine at the level of the glycocalyx.

Effect of phosphocreatine and related compounds on the phospholipid metabolism of ischemic heart.

Changes in the content of lysophosphoglycerides in a crude plasmalemmal fraction of canine heart during short-term ischemia (occlusion of the left descending coronary artery for 8 min) have been studied in the presence and in the absence of phosphocreatine and phosphocreatinine. In the control experiments without PCr or PCr-nine ischemia caused significant elevation of the content of LPG: that of lysophosphatidylcholine was increased by 83% and that of lysophosphatidylethanolamine by 168%. Intravenous administration of PCr and PCr-nine in doses of 300 mg/kg completely prevented accumulation of LPG in the ischemic zone. Because of the well-known arrhythmogenic properties of LPG, the inhibitory effect of PCr and PCr-nine on the elevation of their concentration in the ischemic zone may be closely related to the antiarrhythmic action of PCr and PCr-nine in acute myocardial ischemia.