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Biomedical subjects

E G Krause

Publications and source records attributed to E G Krause.

At least 73 records · Page 4Linked to original sources
PubMed1989

Phosphorylation of phospholamban and troponin I in the ischemic and reperfused heart: attenuation and restoration of isoprenaline responsiveness.

Acute myocardial ischemia maintained for 30 and 60 min with subsequent reperfusion did not induced alterations in the cyclic AMP-mediated phosphorylation capacity of phospholamban and troponin I. Inotropic stimulation of the normal heart with 0.1/uM isoprenaline for 2 min resulted in a simultaneous P-incorporation into phospholamban and troponin I to 44.4 +/- 7.5 pmoles P/mg protein and 42.4 +/- 2.9 pmoles P/mg protein, respectively, assayed by a standardized back-phosphorylation procedure. The adrenergic responsiveness, however, was markedly reduced in the time course of ischemia. After an ischemic period of 60 min the adrenergic-stimulated phosphorylation of phospholamban was diminished to 41 per cent of the control value, whereas the increase of troponin I phosphorylation was completely lost. This differential effect can be discussed in terms of the existence of cytosolic compartments for cA, possessing different lability to ischemic injury of cardiac cells. After post-ischemic reperfusion the isoprenaline responsiveness of the phosphorylation of phospholamban and troponin I was found to be normal demonstrating a reversibility at the level of two important regulator proteins, if the transient ischemia do not exceed 60 min period.

Adenosine Triphosphatases↗
PubMed1989

Partial prevention of calcium paradox in isolated perfused rat hearts by diltiazem.

It is well known that excessive calcium entry into the myocardial cells may contribute considerably to damage of the heart caused by postischemic reperfusion. The effect of increased calcium entry on hemodynamics, energy metabolism and histochemically estimated enzyme activities in isolated, perfused (Langendorff) rat heart preparation was investigated using calcium paradox (CaPX) as a model. After a 15 min period of stabilized perfusion of the heart, CaPX was induced at 37 degrees C by 2.5 min lasting calcium depletion (calcium-free perfusion) and subsequent calcium repletion (10 min). Changes induced by CaPX concerned loss of electrical and mechanical activities of the heart, significant decreases in coronary flow and ATP, ADP and the total content of adenine nucleotides in tissue as well as considerable depression in ATPases, SDH, beta-HBDH, LDH and glycogen phosphorylase activities in the myocardium. Diltiazem in concentration of 4.0 mumol.l-1 applied prior to calcium depletion and during calcium repletion prevented partially the deterioration of cardiac function by improving contractility and electrical activity of the heart as well as the coronary flow. The effect of diltiazem in concentration of 0.4 mumol.l-1 was less expressed. After both concentrations of diltiazem used, a better preserved ultrastructure, higher activities of the enzymes investigated, significantly higher ATP and total adenine nucleotide levels were seen in the myocardium as compared to the untreated controls.

Adenosine Triphosphatases↗
PubMed1989

Immunenzymometric assay for the heart specific glycogen phosphorylase BB in human serum using monoclonal antibodies.

An enzyme-linked immunosorbent assay for the determination of the human glycogen phosphorylase isoenzyme BB (GP BB) using two murine monoclonal antibodies was developed. A series of hybridoma clones producing monoclonal antibodies to GP BB were obtained by the standard lymphocyte hybridoma technique. Two of the selected clones synthesizing monoclonal antibodies, which recognize different epitopes, were employed for the immunenzymometric assay. The first monoclonal antibody was immobilized on microtiter plates and the bound glycogen phosphorylase BB was detected with the second monoclonal antibody conjugated with horse radish peroxidase. This assay enables a specific and sensitive measurement of GP BB in the range of 0.5-150 ng/ml phosphate-buffered saline containing 0.5% bovine serum albumin in less than 3 hours. The lower limit in human serum amounts about 3 ng/ml. Preliminary data obtained with human sera from patients after aorto-coronary artery bypass surgery are demonstrated.

Animals↗
PubMed1989

On the release of glycogen phosphorylase from heart muscle: effect of substrate depletion, ischemia and of imipramine.

The release of glycogen phosphorylase from isolated, perfused rabbit heart was studied after substrate depletion and after global ischemia. The assayed efflux of the enzyme was found to be not only related to alterations in membrane integrity but also to the amount of glycogen in the injured heart tissue. The differential efflux profile of phosphorylase as a constituent of the sarcoplasmic reticulum-glycogenolysis complex in cardiac cells in comparison to cytosolic creatine kinase was found to be more pronounced employing K+-arrested, hypothermically perfused hearts exposed to imipramine (0.4 to 0.6 mM), known for altering specifically membrane integrity. Under these conditions only a rise in the release of creatine kinase occurs, whereas both glycogen content and the efflux of phosphorylase remains uneffected. It is suggested that the metabolical dependence of phosphorylase efflux from the injured heart muscle is of importance for its high sensitivity being a marker of acute heart infarction.

Animals↗
PubMed1989

Improved contractile function in the reperfused rat heart by the radical scavenger 2-[3-aminopropylamino] ethane thiol.

The action of the radioprotector WR 10 65 on regional function of the left ventricular muscle in ischemic injured and reperfused rat heart was investigated employing a new fiber optic based method for determination of segment shortening. In anesthetized rats exposed to regional myocardial ischemia by ligation of the left anterior descending coronary artery for 60 minutes followed by 60 minutes of reperfusion WR 10 65 applicated in a dosage of 1 mM/kg body weight intraperitoneally 30 minutes prior to ischemia induced an improvement of post ischemic recovery of segment shortening from 31% of pre-ischemic values in untreated animals to 64.6%. Because only moderate alterations in global functional parameters compared to control group were found in WR 10 65 treated animals, it is presumed that the observed influence on regional myocardial function is less due to changes in cardiac load than to the radical scavenger activity of the tested agent. A possible contribution of hypoxic and hypocalcemic activity of the substance remains to elucidate.

Animals↗
PubMed1988

Action of iloprost and PGE1 on global ischemic and reperfused myocardium: a 31P-NMR-study.

The influence of iloprost, PGE1 and of the combined application of iloprost and PGE1 on high energy phosphate contents was investigated in isolated rat hearts perfused aerob at 37 degrees C in Langendorff mode. Changes in creatine phosphate, ATP and inorganic phosphate were registered during 20 minutes of global ischemia and 56 minutes of reperfusion with 31P-NMR-spectroscopic methods starting drug application prior to ischemia simultaneously with onset of heart perfusion. Most effective in preservation of high energy phosphates was the combined application of PGE1 and iloprost resulting in a creatine phosphate/inorganic phosphate ratio of 103.2 +/- 30.9% of pre-ischemia values compared to 52.5 +/- 6.1% in control group without drug application 0-5 minutes after onset of reperfusion, 148.8 +/- 24.8% vs 78.8 +/- 15.2% at 6-11 minutes of reperfusion and 116.6 +/- 16% vs 68.9 +/- 12.7% at 12-17 minutes of reperfusion. The same trend was observed employing ATP/inorganic phosphate ratio. The improved energy state in reperfused hearts following application of PGE1 and iloprost in combination is presumed to be supported by a reduction of the loss of high energy phosphates (HEP) during global ischemia and by a cytoprotective effect of iloprost immediately after starting reperfusion.

Alprostadil↗
PubMed1988

Investigations on the mechanism of a diminished inotropic isoprenaline effect in isolated rat hearts after high linoleic acid diet.

Male Wistar rats were fed on a diet rich (13.3 J%) or poor (0.5 J%) in linoleic acid for 10 weeks. The inotropic and chronotropic effects of isoprenaline (100 ng) in isolated perfused hearts were reduced after a linoleic acid rich diet by 36% and 51%, respectively, with an accompanying reduction in isoprenaline-induced increase in the ventricular cAMP content. Moreover, the stimulation of adenylate cyclase in homogenates of ventricular tissue was diminished after linoleic acid rich diet. We postulate that the diminished adrenergic cardiac response after high vs. low linoleic acid diets could be due to alterations in the adenylate cyclase activity and cAMP formation.

Animals↗
PubMed1987

Activation and desensitization of glycolysis by stimulation of adenylate cyclase in rat reticulocytes.

Isoproterenol or forskolin induce a 10-15-fold increase in concentration of cyclic AMP in rat reticulocytes as compared with the basal level of 2.3 +/- 0.3 microM. Glycolysis is stimulated by both compounds transiently more than 2-fold with a peak after 7.5 min followed by an exponential decline. The glycolytic rate in the presence of 10 microM isoproterenol or 10 microM forskolin did not return to basal levels within 60 min of incubation, but was depressed by as much as 50% under the influence of 100 microM forskolin. This phenomenon is designated as metabolic desensitization. The stimulation of glycolysis is probably due to activation of phosphofructokinase as well as to stimulation of Na+,K+-ATPase. The diminished glycolytic flux during the period of metabolic desensitization is accompanied by a decline of glucose 6-phosphate and in the presence of high concentrations of forskolin also by a decrease in glucose 1,6-bisphosphate. A lower rate of influx of glucose is postulated.

1-Methyl-3-isobutylxanthine↗
PubMed1987

Different effect of propranolol and verapamil on isoprenaline-induced changes in the chick embryonic heart.

Isoprenaline (IPRO) has been reported to cause pathological lesions of the embryonic heart. The purpose of the present study was to ascertain whether the development of IPRO-induced changes can be reduced--similarly as in adults--by beta blockade or calcium antagonists. IPRO was administered to 10-day-old chick embryos intraamnially (i.a.) in a dose of 2 X 10 mg.kg-1 per 48 h; propranolol (Inderal) and verapamil (Isoptin) were injected i.a. in a dose of 1.0 or 10.0 mg.kg-1 before each injection of IPRO. It was found that propranolol completely blocked the cardiac IPRO-induced changes, i.e. cardiomegaly, avascular areas and elevation of cAMP. On the other hand, verapamil was found to have no protective effect in any dose used. Furthermore, it increased the mortality of experimental embryos. This fact support the hypothesis that cardiac sensitivity to calcium antagonists may differ during prenatal development.

Animals↗
PubMed1987

The effect of hypoxia on the phosphorylation of contractile and other proteins in perfused rat heart challenged by isoprenaline.

Rat hearts perfused with 32Pi were made hypoxic by perfusion with medium gassed with N2/CO2 (19:1). There was a rapid decrease in tension development (25% of control within 40 s), but little change in the frequency of contraction, time to peak tension, or rate of relaxation. The phosphorylation of troponin-I, C-protein and myosin P-light chain was unaffected by 5 min of hypoxia, whereas the proportions of glycogen phosphorylase and pyruvate dehydrogenase in the active form increased slowly. When aerobically perfused hearts were challenged with a bolus (70 pmole) of D,L-isoprenaline, there was a large increase in contractile force, cyclic AMP concentration, phosphorylation of troponin-I and C-protein and activation of phosphorylase and pyruvate dehydrogenase. Hypoxia for 5 min caused a slight, progressive decrease in the response to isoprenaline of force, cyclic AMP and activation of phosphorylase and pyruvate dehydrogenase. In contrast, there was a larger decrease in the phosphorylation of troponin-I and C-protein, suggesting that the activity of cyclic AMP-dependent protein kinase towards the contractile proteins may be impaired by hypoxia. The phosphorylation of myosin P-light chain was unaltered by any condition. The response to hypoxia is compared to that of ischaemia, where a complete loss of the response to isoprenaline occurs after 5 min.

Animals↗
PubMed1987

Isoproterenol induces both cAMP- and calcium-dependent phosphorylation of phospholamban in canine heart in vivo.

The phosphorylation state of phospholamban in hearts of dogs depleted from catecholamines or treated with isoproterenol has been characterized using a sensitive back-phosphorylation method that allows to distinguish between cAMP-dependent and Ca2+/calmodulin-dependent phosphorylation occurring at the protein in situ. The data obtained demonstrate that in response to the beta-adrenergic agonist isoproterenol both the cAMP-dependent and the Ca2+/calmodulin-dependent phosphorylatable site are phosphorylated suggesting a physiological significance also for Ca2+-dependent phosphorylation of phospholamban in canine heart in vivo.

Animals↗
PubMed1987

Action of trapidil on the heart contractility: relationship to the cyclic nucleotide metabolism.

The relationship between the cardiotonic action of trapidil (RocornalR) and cyclic nucleotide metabolism was studied in the isolated rat heart. The contractility of the heart was increased in a concentration-dependent manner by this drug (ED50 20/microM). Parallel with the mechanical changes the tissue levels of cyclic AMP were increased, which was associated with an activation of the cAMP-dependent protein kinase. Cyclic GMP was enhanced only at a drug concentration of 1 mM. The present findings support the hypothesis that the cyclic nucleotide system is involved in the functional action of trapidil on cardiac tissue.

Animals↗
PubMed1987

Transient activation of cyclic AMP-dependent protein kinase and phosphorylase during the cardiac cycle in the canine myocardium in situ and the effect of propranolol.

The activity ratio of cyclic AMP-dependent protein kinase and glycogen phosphorylase were determined at various stages of the contraction cycle in the canine heart in situ. Both activity ratios vary transiently throughout the contraction-relaxation cycle, the higher values occurring during systole. The rise in the activity ratio of protein kinase was found to coincide with the maximum in the level of cyclic AMP. Propranolol pretreatment prevents the transient in the level of the nucleotide as well as in the activity ratio of the kinase indicating i) a causal relationship between these changes and ii) a neurohumoral, beat-to-beat regulation by catecholamines. Contrary the activity ratio of phosphorylase retains, in the presence of propranolol, its transient changes during the cardiac cycle, probably caused by a Ca2+-mediated activation of phosphorylase kinase during the contraction process.

Animals↗
PubMed1987

A role of adenylate cyclase stimulation in energy metabolism of reticulocytes.

The effects of beta-adrenergic stimulation of adenylate cyclase on energy metabolism of rat reticulocytes were studied. A large initial rate of cAMP formation induced a rapid short-term stimulation of glycolysis which was followed by an exponential decline at maintained high cellular cAMP level. The decrease of glycolytic activity signifies a "metabolic desensitization" by a permanently increased cAMP concentration. Stimulation of PFK activity was found to be the main reason for the increased glycolytic rate which is due to the several fold increase of cAMP and in part to ATP-depletion. Total and coupled respiration, as well as the ATP/ADP ratio were not changed. The data indicate that stimulation of adenylate cyclase of reticulocytes selectively activates glycolysis, i.e. the cytosolic energy compartment with no detectable influence on oxydative phosphorylation.

Adenosine Triphosphate↗
PubMed1987

Immunoinhibition assay of the serum activity of human glycogen isophosphorylase BB in the diagnosis of the acute myocardial ischaemia.

Polyclonal rabbit anti-human isophosphorylases inhibit selectively the isoenzyme activities of the BB and MM isoenzyme of the human glycogen phosphorylase b with high sensitivity and without crossreactivities. On this basis a serological immunoinhibition assay of the BB isoenzyme in the range of 1-125 nmol s-1 l-1 is described. Preliminary clinical results indicate the BB isoenzyme as a sensitive and specific marker of the acute myocardial ischaemia including bypass surgery and suggest a substantial improvement of the differential diagnosis of infarction.

Coronary Disease↗
PubMed1987

Effects of computer controlled submaximal glucose utilization on myocardial energy potential and on survival time during acute strophantin intoxication in dogs.

We checked the effect of a 4 hourly computer controlled submaximal glucose utilization (CCSGU) of 12.01 +/- 1.19 mg/kg min under normoglycaemic conditions and of a simultaneous diminishing of myocardial NEFA supply on trigger mechanism of ventricular fibrillation during acute strophantin intoxication (4 micrograms/kg min) in 17 mongrel dogs. Dogs treated with CCSGU (protective group, n = 8) showed a nearly 30% (p less than 0.01) major survival time (47.6 +/- 3.6 min) before ventricular fibrillation occurred in comparison to a control group (33.1 +/- 3.7 min, n = 9). CCSGU induced a 90% higher left ventricular hydraulic work (5.18 +/- 0.57 Nm/g heart weight) during strophantin infusion compared to controls (2.75 +/- 0.47). No significant myocardial NEFA extraction was evident in the protective group. During CCSGU myocardial oxygen extraction was on a lower level in rest (15.8 +/- 1.0%, p less than 0.01) as well as during strophantin infusion (11.3 +/- 2.6%, p less than 0.01) compared to controls. In dogs treated with CCSGU nearly equal myocardial levels of HEP and lactate were found compared to controls in spite of a major survival time and higher left ventricular hydraulic work. A higher myocardial glycogen content was observed in the protective group (45.1 +/- 6.7 mumol/g w.w.) in comparison to controls (28.1 +/- 2.9, p less than 0.05). Our results prove that CCSGU using the device system GLUCON induces a shift in substrate utilization from NEFA to glucose, decreases myocardial oxygen extraction, increases myocardial glycogen content, enlarges heart work and protects against strophantin induced ventricular fibrillation.

Animals↗