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The relation between action potential configuration and myocardial adenosine triphosphate (ATP) concentration was analysed in isolated low and high work rat heart preparations. Glucose used as sole substrate could not provide total energy production when the isolated hearts performed high work. This may explain the decrease in action potential duration and plateau amplitude (phases 2 and 3) that occurred concomitantly with a low total myocardial ATP concentration. When atrial perfusion was changed to the retrograde mode, however, the action potential configuration was restored without an increase in the global myocardial ATP concentration. Pyruvate used as substrate instead of glucose enhanced ATP production by mitochondrial oxidation and partly restored the action potential modifications (principally phase 2). Adenosine added to glucose in the perfusate or infused in situ (before heart isolation and perfusion) enhanced ATP production by the adenine nucleotide salvage pathway and provided a protective effect for phase 2 and 3 action potential variables.The results using glucose as perfusate showed that there was no correlation between global ATP concentration and myocardial electrical activity. An analysis of the other results suggests that the primary problem in the working heart preparation is that the myocardium is in a state of relative hypoxia or ischaemia and that adenosine merely acts as a coronary vasodilator to improve myocardial oxygen delivery. [ABSTRACT FROM PUBLISHER]

Background: We further explored the role of the elastin–laminin receptor (ELR)-mediated reactions in matrix remodeling and atherogenesis. The progressive increase of life expectancy and the increasing prevalence of diabetes type II motivated the study of the potential influence of extracellular glucose (glc) concentration on ELR-mediated calcium homeostatic reactions as related to atherogenesis. Methods: Most methods using cell cultures were described previously. Glc-variation effects on the vessel wall were studied by tension myography on rat aorta rings and on Ca+-influx using patch clamp technology on endothelial cells. Results: Previous results suggested an important role for the ELR-mediated reactions in vascular remodeling and atherogenesis. Upregulation of elastase-type endopeptidases and free-radical release plays a special role in this respect. Coupling of ELR to NO-synthase (NOS) in endothelial cells results in a vasodilation which is age- and NO-dependent. This effect was shown to vanish at low (0 mM) and high (33 mM) [glc] in adult (6-month-old) rat aortas, but is maintained in old (30-month) aortas at the high [glc]. In addition, Ca+-channel activity (Ba2+ influx) triggered by elastin peptides was maximal at normal [glc] (11 mM) and decreased at lower and higher [glc] in adult aortas. High [glc] was shown also to increase elastase production and the biosynthesis of several matrix components such as collagen III and fibronectin. Conclusions: Our recent results show that high [glc] is a risk factor for ELR-mediated matrix remodeling also. The maintained ELR-NOS coupling in old aortas at high [glc] should further increase ROS-production (free radical release) as shown previously. Superoxide combines with NO yielding the highly toxic peroxinitrite anion with a further increase of degrading protease production. [Copyright &y& Elsevier]

Microfibrils are macromolecular complexes associated with elastin to form elastic fibers that endow extensible tissues, such as arteries, lungs, and skin, with elasticity property. Fibrillin-1, the main component of microfibrils, is a 350-kDa glycoprotein for which genetic haploinsufficiency in humans can lead to Marfan syndrome, a severe polyfeatured pathology including aortic aneurysms and dissections. Microfibrils and fibrillin-1 fragments mediate adhesion of several cell types, including endothelial cells, while fibrillin-1 additionally triggers lung and mesangial cell migration. However, fibrillin-1-induced intracellular signaling is unknown. We have studied the signaling events induced in human umbilical venous endothelial cells (HUVECs) by aortic microfibrils as well as recombinant fibrillin-1 Arg-Gly-Asp (RGD)-containing fragments PF9 and PF14. Aortic microfibrils and PF14, not PF9, substantially and dose dependently increased HUVEC cytoplasmic and nuclear calcium levels measured using the fluorescent dye Fluo-3. This effect of PF14 was confirmed in bovine aortic endothelial cells. PF14 action in HUVECs was mediated by αvβ3 and α5β1 integrins, phospholipase-C, inosital 1,4,5-trisphosphate, and mobilization of intracellular calcium stores, whereas membrane calcium channels were not or only slightly implicated, as shown in patch-clamp experiments. Finally, PF14 enhanced endothelial cell proliferation and migration. Hence, fibrillin-1 sequences may physiologically activate endothelial cells. Genetic fibrillin-1 deficiency could alter normal endothelial signaling and, since endothelium dysfunction is an important contributor to Marfan syndrome, participate in the arterial anomalies associated with this developmental disease.

ATP-sensitive potassium channels (K(ATP) channels) regulate vascular tone and cardiac contraction through their action on the membrane potential of smooth muscle cells and cardiomyocytes. Because aging and diseases alter K(ATP) channel activity, many pharmacological treatments aimed at improving their function, therefore cardiovascular function, have been evaluated. Nicorandil, a K(ATP) channel opener, nitric oxide donor and antioxidant, is used as a treatment of angina pectoris and induces vasodilation, blood pressure decrease and cardioprotection in aging as well as after ischemia-reperfusion. Here, using the patch-clamp technique, we have studied the effect a chronic low dose of nicorandil (0.1 mg/kg per day for 2 months), on the activity of cardiomyocyte K(ATP) channels as a function of age, in newborn, 4-, 12- and 24-month old rats. Nicorandil exerted an anti-oxidant and protective action on cardiomyocyte K(ATP) channels, especially in aged animals, leading to restoration of a normal channel activity. These findings could justify further therapeutical applications.

1. It is known that ATP-sensitive potassium (K(ATP)) channels regulate the membrane potential of smooth muscle cells and vascular tone. Because their activity is altered during ageing, many pharmacological treatments aimed at improving K(ATP) channel and cardiovascular functions have been evaluated. Nicorandil, a K(ATP) channel opener, nitric oxide (NO) donor and anti-oxidant, induces vasodilation, decreases blood pressure and exhibits cardioprotection in ageing, as well as after ischaemia-reperfusion. 2. In the present study, using tension myography and biochemical and histological techniques, we investigated the effects of chronic (2 months) low-dose nicorandil (0.1 mg/kg per day) treatment on the function of rat aorta during ageing (in 4-, 12- and 24-month old rats). 3. The results showed that chronic nicorandil treatment significantly improves mechanical relaxation and noradrenaline-induced vasoconstriction in aged rats. At all ages, the nicorandil-induced vasodilation was primarily mediated by its NO donor group. Nicorandil treatment resulted in an additional 0.5-1 elastic lamella in the aorta and decreased total protein, collagen and elastin content in the aortic wall at all ages. However, in 4-month-old rats, nicorandil significantly increased the elastin : total protein ratio by 19%. 4. In contrast with results of previous studies that used high doses of nicorandil (i.e. 60 mg/kg per day), low-dose nicorandil treatment in the present study did not lead to a progressive desensitization to nicorandil and may be beneficial in improving arterial function in ageing or cardiovascular diseases.

Objective: Sepsis is a potentially life-threatening medical condition induced by viral, bacterial or fungal infection, which is characterized by systemic inflammation, hypotension and vasodilation that can lead to cardiovascular collapse. Increased activity of elastases, enzymes which degrade the extracellular matrix components including elastin, has been demonstrated in plasma of septic patients. Since elastin peptides (EP), by binding to an elastin-laminin receptor on vascular endothelial and smooth muscle cells, induce dose-dependent vasodilation, we hypothesized that elevated circulating EP could contribute to the vasodilation that occurs in septic patients., Materials and Methods: Blood for measurement of EP was collected from not-septic and septic patients admitted to the intensive care unit (ICU), as well as from healthy subjects. Plasma EP concentrations were measured using a competitive ELISA technique., Results: The plasma EP level in the septic patients was approximately half that of the not-septic patients and the healthy controls, with similar EP levels in the latter two groups. There was no apparent association between EP levels and age or gender in any of the groups., Conclusions: Plasma EP levels were actually decreased in septic patients, possibly indicating that the balance between EP production vs. elimination favors elimination. This result further suggests that circulating EP may not be important in the development of the vasodilation and hypotension that occurs in septic shock. Alternatively, however, increased degradation of EP by elastase or other enzymes could lead to the appearance of biologically active EP, which may not be recognized by the ELISA assay.

Glycemia is a physiological parameter tightly regulated for an optimal energetic supply to the organism, in spite of variable tissular glucose needs. Physiopathological alteration of glycemic regulation leads to dysfunctions of many cell types. For example, diabetes considerably increases morbidity and mortality linked to cardiovascular pathologies and constitute nowadays a serious public health problem. Many in vivo and in vitro studies have investigated the impact of extracellular glucose concentration on smooth muscle and endothelial cells. Glycemia regulates expression and activity of proteins implicated in various processes, such as vasodilation (eNOS), cellular adherence (ICAM-1, VCAM-1), glucose transport (GLUT-1) or free radical generation. Nuclear receptors of the PPAR (peroxisome proliferator-activated receptors) family which are implicated in glucose and lipid metabolism control, seem to have direct vascular actions, in the regulation of cellular functions by extracellular glucose, reinforcing their status of pharmacological targets for preservation and improvement of vascular function. More general processes, such as cellular proliferation and cell death, are also influenced by glucose concentration. Concerning the contractile function, hypoglycemia and hyperglycemia modulate vascular reactivity while acting on the vasoactive substances level and the cellular response to these molecules. In particular they act on variation of ionic channels (K+, Ca2+) activity or by interfering with some signaling pathways (NO). For example, the age-dependant vasodilation and endothelial calcium influx induced by elastin peptide are modulated by extracellular glucose levels. In conclusion, abnormal chronic variations of circulating glucose levels seem to be directly responsible for endothelial and smooth muscle cell dysfunction in the pathogenesis of cardiovascular abnormalities of patients presenting glycemia dysregulations.

Elastin peptides have been shown to produce many biological effects on various cell types, including an endothelium- and NO-dependent vasodilatation mediated by extracellular calcium influx and intracellular calcium elevation. Under normal concentration of extracellular glucose, the vasodilatory effect is observed in adult rats and is lost with age. Here, we have studied the consequences of extracellular glucose level changes on these effects triggered by elastin peptides (10(-4)-10(-3) mg ml(-1)), on 6- and 30-month-old rats, using the tension myography and the patch-clamp techniques. Our results show that low (0 mM) or high (33 mM) extracellular glucose concentrations abolish the extracellular calcium influx induced, under normal glucose level (11 mM), by the elastin peptides in cultured human endothelial cells. Also, low or high glucose abolish the vasodilatory action of elastin peptides observed on aorta rings from adult rats under normal glucose concentration. On the contrary, a dilation of aged rat aorta is observed in the presence of elastin peptides and high glucose, whereas such dilation is not observed when the elastin peptides are added in the presence of normal glucose concentration. In aging, a restoration by high glucose of the NO-dependent vasodilatation induced by elastin peptides could enhance the production of damaging peroxynitrite, potentially altering the structure and function of the blood vessels. These results could be of importance in the evaluation and treatment of aged patients with pathophysiological dysregulations of the circulating glucose level, such as in diabetes, age-related glucose intolerance, or low glucose levels caused by inappropriate glucose control treatments.

1. We have tested the effects of 2 month oral treatment with the KATP opener, nitric oxide (NO) donor and anti-oxidant molecule nicorandil (0.1 mg/kg per day) on major physiological parameters and heart function of 4-, 12- and 24-month-old rats. 2. Several methods were used: (i) measurement of blood pressure using a non-invasive tail-cuff method; (ii) perfusion of isolated heart; (iii) lactate dehydrogenase (LDH) dosage; and (iv) measurement of monophasic action potential of rat isolated hearts. 3. Blood pressure and ventricular action potential duration regularly increase with age in control animals, whereas nicorandil restores these parameters in aged animals to levels present in young adult animals. Moreover, following ischaemia, nicorandil treatment improved isolated heart survival rate (100 vs. 50% for nicorandil-treated rats and controls, respectively), heart work and left ventricular developed pressure, whereas it decreased cardiac cell damage (LDH release) and perfusion pressure. 4. This condition of chronic oral nicorandil treatment presents a strong potential in the improvement of cardiac function in normal and pathological ageing.

We have developed a new phosphorescent probe, PdTCPPNa(4), whose luminescence properties are affected by local variations of intracellular oxygen tension (PO(2)). Spectrofluorometric measurements on living human umbilical venous endothelial cells loaded with this molecule show that a decrease in extracellular oxygen tension induces a decrease of PO(2), illustrating the phenomenon of oxygen diffusion and validating the use of this probe in living cells. Moreover, KCN- or 2,4-dinitrophenol-induced modifications of respiration do not lead to detectable PO(2) variations, probably because O(2) diffusion is sufficient to allow oxygen supply. On the contrary, activation by acetylcholine or endothelial nitric oxide synthase (eNOS), which produces NO while consuming oxygen, induces a significant decrease in PO(2), whose amplitude is dependent on the acetylcholine dose, i.e., the eNOS activity level. Hence, activated cytosolic enzymes could consume high levels of oxygen which cannot be supplied by diffusion, leading to PO(2) decrease. Other cell physiology mechanisms leading to PO(2) variations can now be studied in living cells with this probe., ((c)2002 Elsevier Science.)

Bourlier, V., Diserbo, M., Gourmelon, P. and Verdetti, J. Prolonged Effects of Acute Gamma Irradiation on Acetylcholine-Induced Potassium Currents in Human Umbilical Vein Endothelial Cells. Radiat. Res. 155, 748-752 (2001). We have recently reported an acute effect of gamma irradiation (15 Gy, 1 Gy/min) on acetylcholine-mediated endothelium-dependent relaxation in rat aortic rings. Given the importance of permeability to K+ to endothelium-dependent relaxation, we have evaluated the effect of the same radiation on K+ currents in human endothelial cells in culture using the patch-clamp technique in the whole-cell recording configuration. Our results indicate that, in resting cells, gamma irradiation has no effect on endothelial permeability to K+. However, irradiation during stimulation of endothelial cells with acetylcholine reduces the sustained increase in permeability to K+ observed in the acetylcholine-stimulated, nonirradiated cells. Additional experiments using K+ channel inhibitors (TEA, charybdotoxin, apamin) suggest that irradiation may in part decrease the prolonged activation of Ca2+-activated K+ channels by acetylcholine. Taken together with our previous finding that irradiation inhibits the acute relaxing effects of acetylcholine, these results show that gamma irradiation also affects the delayed effects of acetylcholine on permeability to K+.

Vascular endothelial growth factor (VEGF) is mitogenic for endothelial cells and has been shown to induce angiogenesis and endothelial cell migration through stimulation of endothelial tyrosine-kinase receptors. Here, using confocal microscopy and the patch-clamp technique on endothelial cells, membrane permeability to calcium as well as cytoplasmic and nuclear free calcium levels have been investigated in the first stages of tyrosine-kinase receptor activation by VEGF. VEGF (0.5nM) as well as inositol trisphosphate (IP3) induced an activation of membrane calcium-permeable channels exhibiting a similar low conductance in the range of 10 pS. The VEGF-triggered activation of these calcium channels, mediated by IP3 and involving the intracellular calcium stores, results in an increase in both cytoplasmic and nuclear calcium levels in endothelial cells, potentially modulating gene expression. Finally, the effect of Ni2+, a calcium channel blocker, on endothelial cell proliferation has been studied. The results show that inhibition of extracellular calcium influx significantly inhibits VEGF-induced cell proliferation. In the process of cell stimulation by VEGF, and possibly by other growth factors, activation of calcium channels could then be a key step in calcium-regulated gene expression and cell activation. These results suggest that the use of calcium channel blockers could be a novel way of prevention or reversion of VEGF-induced tumoral angiogenesis.

The extracellular matrix protein "elastin" is the major component of elastic fibers present in the arterial wall. Physiological degradation of elastic fibers, enhanced in vascular pathologies, leads to the presence of circulating elastin peptides (EP). EP have been demonstrated to influence cell migration and proliferation. EP also induce, at circulating pathophysiological concentrations (and not below), an endothelium- and NO- dependent vasorelaxation mediated by the 67-kDa subunit of the elastin-laminin receptor. Here, by using the techniques of patch-clamp, spectrofluorimetry and confocal microscopy, we demonstrate that circulating concentrations of EP activate low specificity calcium channels on human umbilical venous endothelial cells, resulting in increase in cytoplasmic and nuclear free calcium concentrations. This action is independent of phosphoinositide metabolism. Furthermore, these effects are inhibited by lactose, an antagonist of the elastin-laminin receptor, and by cytochalasin D, an actin microfilament depolymerizer. These observations suggest that EP-induced signal transduction is mediated by the elastin-laminin receptor via coupling of cytoskeletal actin microfilaments to membrane channels and to the nucleus. Because vascular remodeling and carcinogenesis are accompanied by extracellular matrix modifications involving elastin, the processes here described could play a role in the elastin-laminin receptor-mediated cellular migration, differentiation, proliferation, as in atherogenesis, and metastasis formation.

1. To determine the acute effects of irradiation on the functionality of vessel, rat aortic rings were mounted in an organ bath for isometric tension measurements and irradiated (60Co, 1 Gy min(-1), 15 min). 2. Irradiation, which is without effect on non-contracted or endothelium-denuded vessels, led to an immediate and reversible increase in vascular tone on (-)-phenylephrine (1 microM)-precontracted aortic rings. The tension reached a plateau about 5 min after the beginning of irradiation. 3. The maximal radiation-induced contraction occurred on aortic rings relaxed by acetylcholine (ACh) (1 microM). In this condition, the addition of catalase (1000 u ml(-1)), which reduces hydrogen peroxide, and DMSO (0.1% v/v), which scavenges hydroxyl radical, had no influence on tension level while superoxide dismutase (SOD) (100 u ml(-1)), a superoxide anion scavenger, reduced the observed contraction. A similar result was obtained in the presence of indomethacin (10 microM), a cyclo-oxygenase blocker. 4. Pretreatment of rings with the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME) (10-100 microM) inhibited the radiation-induced contraction. 5. This effect was dose rate-dependent and even occurred for a very low dose rate (0.06 Gy min(-1)). 6. The present results indicate that gamma-radiation induces an instantaneous vascular tone increase that is endothelium and dose rate-dependent. This effect is (i) maximal when nitric oxide (NO) is produced, (ii) greatly reduced by SOD and (iii) inhibited by L-NAME, suggesting a major involvement of complexes between NO and superoxide anion.

The elastic properties of extensible tissues such as arteries and skin are mainly due to the presence of elastic fibers whose major component is the extracellular matrix protein elastin. Pathophysiological degradation of this protein leads to the generation of elastin peptides that have been identified in the circulation in the ng/mL to microg/mL range. Similar concentrations of an elastin peptide preparation (kappa-elastin) were previously demonstrated to induce, among other biological actions, a dose- and endothelium-dependent vasorelaxation mediated by the elastin/laminin receptor and by endothelial NO production. To determine the elastin sequence(s) responsible for vasomotor activity and to learn more about possible signaling pathways, we have compared the action of different concentrations (10(-13) to 10(-7) mol/L) of recombinant human tropoelastin, eight synthetic elastin peptides, and a control peptide (VPVGGA) on both rat aortic ring tension and [Ca2+]i of cultured human umbilical vein endothelial cells. No vasoactivity could be detected for VPVGGA and for the elastin-related sequences VGVGVA, PGVGVA, and GVGVA. Tropoelastin, VGV, PGV, and VGVAPG were found to induce an endothelium- and dose-dependent vasorelaxation and to increase endothelial [Ca2+]i, whereas PVGV and VGVA produced these effects only at low concentration (10(-11) mol/L). A likely candidate for mediating the elastin peptide-related effects is the elastin/laminin receptor, since the presence of lactose strongly inhibited the vasoactivity associated with these compounds. Our results show that although the flanking amino acids modulate its activity, VGV seems to be the core sequence recognized by the elastin receptor.

The protective effect of heat stress against mechanical dysfunction and myocardial necrosis after prolonged ischemia is well known. We have investigated whether the protective effect of heat stress extends to reperfusion arrhythmias in the isolated perfused rat heart. Rats were exposed to 20 min of 42 degrees C hyperthermia. Twenty-four h later their hearts were isolated, perfused and subjected to a 5-min period of occlusion of the left coronary artery. The incidence and duration of reperfusion arrhythmias were assessed in the 30-min reperfusion period. Prior heat stress led to a reduction in the incidence (from 100 to 60%, P

Basic fibroblast growth factor (bFGF) has been implicated in the changes in gene expression that, under pathological conditions such as ischemia or volume overload, lead to adult cardiomyocyte hypertrophy. In many tissues, one of the first events following cell activation by growth factors is an enhancement of the intracellular free calcium concentration, generated by fluxes from internal storage compartments and through channels of the plasma membrane. The present study was undertaken to determine whether cardiac myocytes isolated from adult rat ventricles express Ca2+-permeable channels activated by bFGF. Using the cell-attached mode of the patch-clamp technique, we observed that bFGF (from 0.1-10 nM) induced an increase of fast burst openings, mediated by Ca2+-permeable channels with low conductance (15 pS) and voltage-independence. Inside-out patch-clamp experiments revealed that inositol 1,4,5-trisphosphate (5 microM) enhanced the opening of Ca2+-permeable channels with similar properties as the bFGF-induced channels, indicating that IP3 may be a second messenger of this process. Confocal fluorescence imaging of intracellular free calcium provided direct evidence that bFGF induced an increase of cytoplasmic and nucleoplasmic free Ca2+ concentrations which were generated, in part, by Ca2+ influx through the plasma membrane. In conclusion, this study supports the presence, in the plasma membrane of adult cardiac myocytes, of messenger-activated calcium channels which could play key roles in the calcium-dependent pathways that are activated in response to growth factors., (Copyright 1997 Academic Press Limited.)

The nuclear envelope possesses specific ion channels that regulate the ionic traffic between the cytoplasm or the perinuclear space and the nucleoplasm. Using the patch-clamp technique to isolated rat nuclei exhibiting only the inner membrane of the nuclear envelope, we report the existence of calcium and zinc permeant channels. These channels displayed similar characteristics (conductance : 8 and 11 pS respectively, open time constant (3.5 ms and 3.7 ms) and close time constant (5.1 ms and 4.8 ms)) and were insensitive to different types of calcium channels blockers and to calcium concentration in the bathing solution. The exact role of these channels remains to define, but they may contribute to the regulation of intranuclear Ca++ or Zn++ dependent processes as important as cell proliferation or programmed cell death. Moreover, this work demonstrates that our nuclei preparation provides a way to study the inner membrane of the nuclear envelope.

Using patch-clamp single channel recording techniques, we reported a Platelet-Activating Factor "PAF"-induced activation of large conductance Ca(2+)-activated K+ "BK(Ca)" channels in N1E-115 cells. This activation was only observed in cell-attached configuration and was blocked by the PAF antagonist BN50739 or removal of calcium from the bath. Nanomolar concentration of PAF produced a transient hyperpolarization observed in whole-cell current clamp configuration which was blocked by the bath application of BN50739 or iberiotoxin. Our results suggest that the PAF-induced hyperpolarization is mediated by an activation of BK(Ca) channels coupled to specific PAF receptors. This coupling is not direct and results from the PAF-induced elevation in cytosolic free Ca2+ concentrations that we have previously described in N1E-115 cells (Cell Calcium 1995, 17, 442-452).

A series of substituted-1,2,4-benzothiadiazin-1,1-dioxide derivatives was designed and synthesized as potassium channel modulators. Various sulfonylurea moieties were introduced on positions 3 and 7 of the heterocycle without, or by means of, methylene and phenyl spacers. On rat aortic rings, several compounds displayed vasodilating activities, especially compound 24, which was more active than cromakalim and diazoxide at low doses (0.1 microM) and more active than diazoxide between 1 and 10 microM.

The aim of this study was to determine the extent and location of damaged myocardial areas in senescent rats. The viability of myocardial cells was evaluated in virgin young (4 months old) and aged (29 months old) female Wistar rats by analysing the uptake of a slowly metabolisable radiolabelled fatty acid analogue, 15-p-iodophenyl-beta-methylpentadecanoic acid (IMPPA). The biodistribution of IMPPA was measured in various organs, and regional myocardial uptake was specifically assessed using quantitative autoradiography. Myocardial enzymatic activity and DNA content were also evaluated with nitro blue tetrazolium (NBT) and propidium iodide (PI) staining, respectively. In senescent rats, cardiac and renal IMPPA uptake showed a significant (50%) reduction compared with young adult rats and the uptake was not significantly changed in the liver, spleen, lungs, and skeletal muscle. Total ventricular NBT staining and IMPPA uptake were almost homogeneous in young adult rats, whereas they were very heterogeneous in aged rats. In the latter, approximately 11% of the total ventricular volume showed a significantly decreased (by 60% or more) IMPPA uptake compared with normal values, and this reduction was greater in ventricle base than in apex. The myocardial areas unlabelled or poorly labelled by IMPPA represented 4, 5, 6, and 21% of the right ventricular, left ventricular epicardial, septal, and left ventricular endocardial volume, respectively, and were poorly stained with NBT. In some of these areas, PI staining indicated the presence of living cells unable to pick up NBT staining. In conclusion, in young adult rats, no myocardial lesions were observed using three different labelling techniques.(ABSTRACT TRUNCATED AT 250 WORDS)

The elastin-laminin receptor was shown to be present on several benign and malignant cell types and to mediate several important cell reactions such as chemotactic movements of fibroblasts and monocytes, release of lytic enzymes and oxygen free radicals from leucocytes, increased adhesion of mesenchymal cells to elastin fibers as well as modifications of ion fluxes-increase of calcium and sodium influxes and decrease of ouabain-dependent potassium influx. We now demonstrated that the addition of elastin peptides to rat aorta rings precontracted with noradrenaline produced an endothelium-dependent vasorelaxation. The inhibition of this effect by laminin and lactose is in favor of the mediation of this action of elastin peptides by the 67 kDa subunit of the elastin-laminin receptor which possesses a lectin site. As elastin peptides are present in the circulating blood and their concentration was shown to increase in some pathological conditions, this phenomenon may well have physiopathological significance.

New methods are described to detect subconductance levels and to analyse ion channel gating. These methods are applied to simulated and experimental data. Single chloride channel records from inside-out membrane patches excised from human umbilical venous endothelial cells (HUVEC) exhibit, in addition to the full closed and full open configurations, intermediate subconductance levels which are multiple of an elementary conductance of 112.5 pS. Analysis of transitions from one state to another and the comparison of real data with simulated data leads to the proposal of a cooperative model of gating for the observed subunits of a chloride channel.

The dynamics of cardiac adenine and uracil nucleotides, following a subcutaneous injection of isoproterenol, was studied on the rat in vivo. The effect of continuous supply of adenosine, uridine, or ribose on the level of ATP and UTP was investigated on control rats and on isoproterenol-treated animals. The precursors were administered by continuous infusion (1 ml.h-1) into the superior caval vein. 1. ATP and UTP levels were decreased within one hour after a single dose of isoproterenol (5 mg.kg-1) (Fig. 1). 2. Then, the level of ATP rose slowly toward the control value. The normal level was not reached within 48 h (Fig. 1). 3. On the contrary, the initial drop in UTP concentration was followed by a rapid restoration. The control value was reached in 3 h, and then the UTP pool was increased to 180% of the normal level, 12 h after isoproterenol application. 4. As previously shown by other authors, the restoration of ATP was accelerated by a continuous supply of adenosine (37 micromoles per hour) or ribose (170 micromoles per hour) (Fig. 2). 5. The infusion of ribose (170 micromoles per hour) or uridine (41 micromoles per hour) completely suppressed the initial decrease in UTP level caused by beta-receptor stimulation. The further enlargement of the UTP pool was greatly enhanced by ribose or uridine (Fig. 3). 6. The infusion of adenosine was also positive on UTP regeneration. On the contrary, uridine had no effect on the ATP pool (Fig. 3). 7. When supplied to non-treated animals, all precursors caused an enhancement of the UTP level. Adenosine and ribose increased the ATP pool (Fig. 2 and 3). These results contribute to the comparison of the efficiency of the various pathways of cardiac nucleotide synthesis. They show that both de novo synthesis and salvage pathways are limited by the amount of precursors. The increase in UTP synthesis caused by ribose is consistent with the theory put forward for purines (ZIMMER et GERLACH, 1974) that phosphoribosyl-pyrophosphate availability limits the efficiency of de novo synthesis of nucleotides; it demonstrates that this concept is also true for de novo synthesis of pyrimidine nucleotides.

Mechanical performance and tissue content of high-energy phosphates were studied in working rat hearts, isolated from normal rats, or from daily subcutaneously injected with isoproterenol for one day or seven days (5 mg/kg b.w.) and atrially perfused. Isoproterenol pretreatment led to a significant decrease in myocardial content of ATP, ADP. After 75-min perfusion, the content of ATP, ADP, AMP and CP was significantly lower in pretreated hearts than in untreated. On the other hand, isoproterenol-treated hearts exhibited higher aortic pressure, oxygen consumption, left ventricular systolic pressure and d (L.V.P.) max/dt and heart work. It is suggested from these findings that isoproterenol pretreatment of rats improve cardiac work and decrease efficiency in ISO.24 h group and improve cardiac work and efficiency in ISO.7 days group.

1. Age-related changes in electrophysiological and pharmacological properties of rat ventricular cells have been investigated. 2. As compared to adults, transmembrane action potential (TAP) of aged rat myocardium exhibits a prolonged phase of repolarization. 3. For both young and aged groups tetrodotoxin reduces TAP duration. 4. Nifedipine and isoproterenol induce more pronounced modifications of the TAP in aged subjects. 5. Amiloride and tetraethylammonium ions prolong, for both groups, phase 2 of repolarization. This effect is more marked in the aged group. 6. Our results suggest that the prolonged TAP in aged myocardium could result from an age-related increase in calcium current.

14C adenine was supplied to isolated Rat heart retrograde perfused. The experiment was continued by aortic or atrial perfusion and the evolution of the specific radioactivity of ATP was estimated. Aortic perfusion did not reduce ATP content and the specific radioactivity decreased, expressing the turnover of adenine nucleotides. On the contrary, working heart perfusion provoked a breakdown of ATP and an increase of ATP specific radioactivity. When myocardial ATP was decreased prior to the perfusion with isoproterenol, the incorporation of 14C adenine was enhanced, a further aortic perfusion induced a greater decrease of ATP specific activity than in controls. Atrial perfusion did not change the concentration and the specific activity of ATP. These data seem to provide experimental evidences for a compartmentalization of myocardial ATP.

Glutathione peroxidase (GSh-Px), superoxide dismutase (SOD), catalase (CAT) activities and malon-dialdehyde (MDA) content were determined in heart, liver, kidney and brain of rats. Two different age groups (4 months; 24 months) were considered. GSH-Px and SOD activities decrease significantly for the aged liver and kidney. During aging, the activity of catalase increase in cardiac muscle and, in contrast, decrease in other organs. Lipids peroxidation, expressed in term of MDA formation, decrease in all the organs of the aged rats. The results indicate that: 1) the liver and kidney antioxidative defense decrease with age; 2) the enzymatic activities evolve in a different manner for different enzymes and organs. Furthermore, the results suggest that there is not any correlation between the SOD, CAT, and GSH-Px activities and the peroxidative status of the organs; thus, the age-related increase in the MDA content proposed as a criterion of aging process should be considered with caution.

In this work, we compared the electrophysiological and metabolic parameters of a volume overload model of cardiac hypertrophy (aorto-caval fistula) with those of two other models of hypertrophy (aortic stenosis and isoproterenol pretreatment). In these last models, a prolongation of action potential and a decrease of myocardial ATP content are observed. However, these alterations are not shown in the aorto-caval fistulated animals while their heart are well hypertrophied. The amplitude increase of phase 3 AP seemed to be a common factor of these models of cardiac hypertrophy.

5 hrs after a single sub-cutaneous injection of the drug in a dose of 5 mg/kg, the ATP concentration was reduced by 15%, the incorporation of 14C adenine was augmented by 20% and the turnover of ATP was accelerated: the reduction of specific radioactivity attained 16%, 75 mn after the period of marquage, instead of 7% in the control hearts. When the drug was added to the perfusion fluid, there was no supplementary reduction of the ATP concentration and the action on the nucleotide turnover only existed if the ATP level was reduced by a pretreatment: the reduction of specific radioactivity then attained 24% after 75 min. of perfusion.