Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We evaluated the contributions of calcium loading and impaired energy production to metabolic and ultrastructural manifestations of cell injury in a cultured neonatal rat ventriculocyte model. Direct calcium loading was produced by incubation in K(+)-free medium to inhibit the Na+,K(+)-ATPase and promote Na(+)-Ca2+ exchange, and inhibition of energy metabolism was produced by incubation with 30 microM iodoacetic acid (IAA). Measurements were made of total cell calcium, [3H] arachidonic acid (AA) release (an index of membrane phospholipid degradation), ATP, and ultrastructural features of cell damage. Inhibition of the Na(+),K(+) pump resulted in the rapid onset of cellular calcium loading, increased [3H]AA release, and moderate ATP reduction. After return to control medium for 24 hours, myocytes previously exposed to K(+)-free medium for 1 hour showed recovery of ATP level and little additional [3H]AA release. However, after 2 to 3 hours of calcium loading, the ATP level remained moderately depressed, residual [3H]AA release was greater, and a mixed population of relatively normal and severely damaged myocytes was observed by electron microscopy. IAA treatment for 1 hour resulted in moderate ATP reduction without calcium accumulation or [3H]AA release, whereas IAA treatment for 3 hours resulted in marked ATP reduction associated with calcium accumulation and [3H]AA release. Reversal experiments showed substantial recovery of ATP level after 1 hour of IAA exposure, and marked ATP depression and [3H]AA release associated with widespread irreversible injury after 3 hours. Thus, the data indicate that increased calcium accumulation itself can initiate accelerated membrane phospholipid degradation, but that progression to irreversible injury is influenced by other factors, including the magnitude of ATP depression associated with calcium loading.
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PMID:Effects of calcium loading and impaired energy production on metabolic and ultrastructural features of cell injury in cultured neonatal rat cardiac myocytes. 216 2

1. We previously isolated an extract from porcine left ventricle that possessed digitalis-like properties such as inhibition of cardiac and kidney Na+, K(+)-ATPase, displacement of [3H]-ouabain from its binding sites and cross reactivity with digoxin antibodies. The extract also had a positive inotropic effect on the guinea-pig heart. 2. In the present study the positive inotropic response of the extract was characterized in canine right ventricular trabeculae. Maximum inotropic response (501 +/- 20%) was produced by 300 microliters and the half maximal increase occurred with 125 microliters of the extract. 3. Ouabagenin produced aftercontractions in rapidly paced trabeculae. Equipotent and even greater amounts of the extract did not produce aftercontractions. 4. The extract increased the amplitude of the delayed component (P2) of biphasic contractions produced by replacing about 92-96% of the external Ca with Sr. A smaller increase in the size of the early component (P1) was also seen. 5. The extract decreased post-rest potentiation after rest for 30s and 2 min. After 8 min of rest, post-rest potentiation was converted to post-rest depression. 6. The extract (20 microliters) produced a decrease in the amplitude of the post-rest rapid cooling contracture (RCC) at all rest intervals. The steady state RCC, although greater than that in the control muscle, was increased to a lesser extent than the size of the steady state electrically driven contractions. 7. It is suggested that the extract from porcine left ventricle produces a positive inotropic response by increasing the trans-sarcolemmal influx of Ca. It also has additional effect(s) on the sarcoplasmic reticulum in that it may facilitate the loss of Ca from the sarcoplasmic reticulum and/or inhibit the uptake of Ca by the organelle.
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PMID:Positive inotropic effect of porcine left ventricular extract on canine ventricular muscle. 225 39

This study tested the hypothesis that membrane transport is the major biochemical system of the myocardium altered in furazolidone-induced cardiomyopathy (round heart disease), before the development of myocardial failure, and that metabolic enzymes and contractile proteins are less affected. Compared with controls, maximal percentage depression of activities of myocardium from furazolidone-treated birds were 40 for creatine kinase, 30 for glycolysis, 30 for glycogen, 20 for myofibrils, 20 for Krebs's cycle enzymes, 15 for fatty acid oxidation and 10 for total soluble protein. Sodium and potassium transport, antioxidant system activity, myosin, myosin isoenzyme patterns and amino acid aminotransferases were unaffected. In marked contrast, the calcium-transport ATPase activity of the sarcoplasmic reticulum had undergone a 60 per cent compensatory increase in activity. The pattern of biochemical changes observed is consistent with a role of ischaemia in the pathogenesis of round heart disease and indicates that calcium transport by the sarcoplasmic reticulum is the major biochemical system affected.
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PMID:Myocardial biochemical changes in furazolidone-induced cardiomyopathy of turkeys. 232 37

Rats were injected intraperitoneally with 40 mg/kg body weight isoproterenol and the heart sarcolemma was isolated 3, 9 and 24 hours later. The heart/body weight ratio increased and varying degrees of change in cardiac ultrastructure were apparent at 9 and 24 hours after isoproterenol injection. Na+-dependent Ca2+ uptake activities of heart sarcolemma were depressed at 3, 9 and 24 hours; such alterations in 24 hour preparations were evident at different times of incubation and at different concentrations of Ca2+. No differences in Na+-induced Ca2+ release or Na+-K+ ATPase activities were observed between the control and experimental membranes. The control and isoproterenol-treated heart sarcolemmal preparations were minimally but equally contaminated by other subcellular organelles. Although there was no significant change in the phospholipid composition, the protein pattern as determined by gel electrophoresis was altered in sarcolemma at 24 hours of isoproterenol treatment. These results indicate an abnormality of heart sarcolemmal Na+-dependent Ca+ uptake during the development of catecholamine-induced cardiotoxicity. It is suggested that a depression in the ability of the cell to remove Ca2+ through the Na+-Ca2+ exchange in sarcolemma may contribute to the development of intracellular Ca2+ overload in catecholamine induced cardiomyopathy.
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PMID:Alterations of sarcolemmal Na+-Ca2+ exchange in catecholamine-induced cardiomyopathy. 241 73

Current theories of the causes of somatic symptoms in depression neglect evidence for a general inhibition of Na,K-ATPase. Experimentally, sodium pump inhibition is associated with depolarization of electrically active tissue: the threshold of peripheral nerves is decreased and smooth muscle function altered. Symptoms compatible with these changes are found both in depression and intoxication with digoxin, which inhibits Na,K-ATPase. The hypothalamus contains inhibitors of Na,K-ATPase which are capable of producing depolarization. In depression, changes in hypothalamic activity may increase endogenous inhibition and contribute to the somatic symptoms.
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PMID:Disturbed hypothalamic control of Na,K-ATPase: a cause of somatic symptoms of depression. 242 32

Ca2+ pump activity of skeletal muscle microsomes containing fragments of sarcoplasmic reticulum was examined in rats 8 wk after the induction of chronic diabetes by an intravenous injection of streptozotocin (65 mg/kg). In comparison with the control values, both ATP-dependent Ca2+ uptake and Ca2+-stimulated ATPase activities were increased in the microsomal fraction from diabetic rats. These changes were seen as early as 7 days after streptozotocin injection and were apparent at various times of incubation (1-10 min) as well as at different concentrations of free Ca2+ (10(-7)-5 X 10(-5) M Ca2+). Insulin administration to diabetic animals for 2 wk reversed Ca2+ uptake and ATPase activities to control levels. The increase in microsomal ATPase activity of the diabetic preparation due to cAMP-dependent protein kinase or calmodulin was greater than in the control microsomes and the depression by a specific inhibitor of protein kinase, but not of calmodulin, was greater in diabetic muscle. The enhanced Ca2+ pump activity was associated with altered phospholipid composition and protein profile of the diabetic preparations. The rate of Ca2+ release from microsomal vesicles was unaffected by the diabetic condition. Isometric contractile force development as well as positive dF/dt and negative dF/dt of the skeletal muscle from diabetic animals were higher at different pulse strengths (0.5-100 V) and at different Ca2+ concentrations (0.25-2.5 mM). These results suggest that diabetes is associated with enhanced sarcoplasmic reticular Ca2+ pump activity, and this may account for the hyperfunction of skeletal muscle in this disease.
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PMID:Calcium pump activity of sarcoplasmic reticulum in diabetic rat skeletal muscle. 243 Apr 66

Emotional-painful stress in rats was shown to decrease insignificantly transmembrane cardiomyocyte potential (TCP) measured in isolated hearts. The recovery of TCP following its depression due to the preparation cooling was twice slower in stress-exposed than in control animals. This is in keeping with the data on stress-induced disturbances of Na, K-ATPase activity (an enzyme playing a leading role in TCP maintenance). It is suggested that the disturbance in cation pump function activity plays a certain role in the onset of arrhythmias and cardiac fibrillation during stress.
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PMID:[Effect of stress on the cardiomyocyte transmembrane potential of the working heart and its recovery after hypothermia]. 243 58

Perfusion of isolated rat hearts for 10 min with substrate-free hypoxic medium resulted in a depression of sarcolemmal Na+-dependent Ca2+ uptake, Ca2+-stimulated ATPase, ATP-dependent Ca2+ uptake and Na+-K+ ATPase in sarcolemma. Reoxygenation of these hearts resulted in a further depression of all these activities. Na+-induced Ca2+-efflux was unaffected in vesicles of hearts subjected to hypoxia-reoxygenation. Developed contractile force and resting tension in hypoxic hearts were 15% and 400% of control values, respectively, while reoxygenation was associated with a slight recovery of developed contractile force and the resting tension was lowered appreciably but remained elevated. Because sarcoplasmic reticular Ca2+ uptake and mitochondrial Ca2+ uptake were depressed under similar conditions, cellular injury due to hypoxia-reoxygenation was not specific to the sarcolemma. These results indicate that inability of the ischemic heart to recover its function may be associated with defects in Ca2+-transport systems.
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PMID:Irreversible damage to sarcolemmal Ca2+ transport in myocardial ischemia. 244 89

The voltage- and time-dependent slow channels in the myocardial cell membrane are the major pathway by which Ca2+ ions enter the cell during excitation for initiation and regulation of the force of contraction of cardiac muscle. These slow channels appear to behave kinetically, on a population basis, as if their gates open, close, and recover more slowly than those of the fast Na+ channels. In addition, the slow channel gates operate over a less negative (more depolarized) voltage range. Tetrodotoxin does not block the slow channels, whereas the calcium antagonistic drugs, Mn2+, Co2+, and La3+ ions do. The slow channels have some special properties, including functional dependence on metabolic energy, selective blockade by acidosis, and regulation by the intracellular cyclic nucleotide levels. Because of these special properties of the slow channels, Ca2+ influx into the myocardial cell can be controlled by extrinsic factors (such as autonomic nerve stimulation or circulating hormones) and by intrinsic factors (such as cellular pH or ATP level). During transient regional ischemia, the selective blockade of the slow channels, which results in depression of the contraction and work of the afflicted cells, might protect the cells against irreversible damage by helping to conserve their ATP content. Reperfusion arrhythmias may be caused by the breakdown of this protective mechanism, in that, upon reperfusion, the Ca2+ slow channels may recover before the cells are capable of handling the greater Ca2+ influx (Fig. 20). As depicted in this figure, the Ca2+ slow channels may recover their function before the ATP level is sufficiently recovered to allow bail-out of the intracellular Ca2+. In addition, the generation of free radicals upon reperfusion may injure the Ca-ATPase and other enzymes involved in Ca2+ metabolism. The net effect of this would be to cause Ca2+ overload of the cells and SR, with subsequent delayed after-depolarizations (DADs) leading to triggered automaticity and arrhythmias. Following blockade of the fast Na+ channels in myocardial cells with TTX or by voltage-inactivating them in 25 mM (K)0, catecholamines, angiotensin-II, histamine, and methylxanthines rapidly allow the production of slowly-rising Ca2+-dependent action potentials by increasing the number of Ca2+ slow channels available for voltage activation and/or their mean open time. Concomitantly, these compounds rapidly elevate intracellular cyclic AMP levels, suggesting that cyclic AMP is somehow related to the functioning of the slow channels. Exogenous cyclic AMP produces the same effect, but much more slowly.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Regulation of calcium slow channels of cardiac muscle by cyclic nucleotides and phosphorylation. 245 7

Monoclonal antibodies against gizzard smooth muscle myosin were generated and characterized. One of these antibodies, designated MM-2, recognized the 17-kDa light chain and modulated the ATPase activities and hydrodynamic properties of smooth muscle myosin. Rotary shadowing electron microscopy showed that MM-2 binds 51 (+/- 25) A from the head-rod junction. The depression of Ca2+- and Mg2+-ATPase activities of myosin and Ca2+-ATPase activity of heavy meromyosin at low KCl concentration were abolished by MM-2. Viscosity measurement indicated that MM-2 inhibits the transition of 6 S myosin to 10 S myosin. While the rate of the production of subfragment-1 by papain proteolysis of 6 S myosin was inhibited by MM-2, the rate of proteolysis of the heavy chain of 10 S myosin was enhanced by MM-2 and reached the same rate as that of 6 S myosin plus MM-2. These results suggest that MM-2 inhibits the formation of 10 S myosin by binding to the 17-kDa light chain which is localized at the head-neck region of the myosin molecule. MM-2 increased the Vmax of actin-activated Mg2+-ATPase activities of both dephosphorylated myosin and dephosphorylated heavy meromyosin about 10- and 20-fold, respectively. MM-2 also activated the actin-activated Mg2+-ATPase activity of phosphorylated myosin at a low MgCl2 concentration and thus abolished the Mg2+-dependence of acto phosphorylated myosin ATPase activity. These results suggest that MM-2 inhibits the formation of 10 S myosin, and this results in the activation of actin-activated Mg2+-ATPase activity even in the absence of phosphorylation.
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PMID:Inhibition of conformational change in smooth muscle myosin by a monoclonal antibody against the 17-kDa light chain. 246 45


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