摘要:

Little is known about the possible role of leukocytes in the pathogenesis of vasospasm. We hypothesized that vasoactive products released by leukocytes might produce constriction of atherosclerotic arteries. To test this hypothesis, we infused fmet-leu-phe (fMLP), a peptide that activates leukocytes to release their vasoactive products, into the perfused hind limb of normal and atherosclerotic cynomolgus monkeys. Infusion of fMLP did not change resistance of large arteries in normal monkeys. In contrast, fMLP produced pronounced constriction of large arteries in atherosclerotic monkeys. To determine whether leukotrienes, platelet-activating factor, or prostaglandin E2(PGEJ2which are released by leukocytes, may contribute to leukocyte-induced vasoconstriction in atherosclerotic monkeys, we injected leukotriene D49platelet-activating factor, and PGE2intra-arterially into the perfused hind limb. Leukotriene D4and platelet-activating factor had minimal effects on large arteries in both normal and atherosclerotic monkeys. PGE2produced marked constriction of large arteries in atherosclerotic, but not normal, monkeys. Thus, pronounced constriction in atherosclerotic, but not normal, arteries during infusion of fMLP suggests that products released by leukocytes may mediate vasoconstriction in atherosclerotic vessels. Vasoconstrictor responses to PGE2are profoundly potentiated by atherosclerosis, which suggests that PGE2may contribute to leukocyte-induced vasoconstriction.

ISSN:0009-7330    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Myocardium is generally thought to express no more than two isoforms of troponin T (TnT). We have recently reported that TnT purified from rabbit myocardium is resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis Into five proteius (TnT1, TnT2, TnT3, TnT4, and TnT5). In this study, these proteins are characterized immunologically and a novel elaborate maturational profile is described. Myocardium was obtained from 23 days of gestation fetal rabbits and 2-day, 6-week, 3-month, and 6-month postnatal rabbits. The major species in the adult myocardium, TnT4, was identified on sodium dodecyl sulfate-polyacrylamide gels and excised. The protein was electroeluted and purified. An amino acid microsequence of a cleaved fragment of this protein was found to be virtually identical to residues 86-99 from adult rabbit cardiac TnT. The protein, TnT1, was used to raise a polyclonal antibody. This antibody recognized all five isoforms from purified cardiac TnT, but none of the TnT isoforms from fast skeletal muscle. A monoclonal antibody, Mab JLT-12, raised against a highly conserved epitope of rabbit fast skeletal muscle, recognized all five cardiac as well as five skeletal muscle isoforms. Western blots performed on intact myocardial preparations demonstrated that TnT1the cardiac isoform with the slowest electrophoretic mobility, was expressed prominently in the immature hearts, in addition to TnT2, TnT3, and TnT4, but TnT1was not evident in the 3-month and 6-month postnatal hearts. The expression of TnT2also decreased with maturation. Thus, the number of TnT isoforms expressed in the rabbit decreases with maturation. These results demonstrate a greater heterogeneity of expression of cardiac TnT isoforms than was previously suspected and suggest that all the five identified TnT rabbit cardiac isoforms are derived from a different gene than the fast skeletal muscle TnT gene. Sequencing of the rabbit cardiac TnT gene(s) and complementary DNA analysis are needed to establish fully the molecular basis of these five cardiac TnT isoforms.

ISSN:0009-7330    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

We have previously studied the relation between long-chain fatty acid and pyruvate metabolism in reperfused myocardium and noted a rapid return of fatty acid oxidation to at least preischemic values accompanied by a marked decrease in pyruvate oxidation. The purpose of the present report is to further characterize carbohydrate metabolism during reflow by describing rates of glucose oxidation using [6-14C]glucose. Chddative performance was determinedwith and without preserved fatty acid utilization; the latter condition was effected byoxfenicine, which inhibits palmitoylcarnitine transferase I. In the main protocol, two groups ofworking swine hearts (n=18) were perfused aeroblcaUy for 30 minutes, rendered regionallyischemic (−60 Δ% in anterior descending coronary flow) for 45 minutes, and reperfused atcontrol flows for a final 50 minutes of perfusion. An emulsion of Intralipid with heparin wasadministered systemically throughout the studies to augment serum fatty acids (average fattyacid values, 1.05 ± 0.05 μmol/ml for both groups). Serum glucose was monitored and maintainedat or about 100 rag/dl with additional infusions of glucose as needed. Oxfenicine (33mg/kg) was administered systemically by bolus injection at time 0 and 60 minutes of perfusionin nine animals. Decreased mechanical performance, that is, stunning, during reflow wasevident in both groups (−50 Δ% in regional systolic shortening,p< .0.05 compared with aerobicvalues in the control group, and -32 Δ%,p≤ 0.05 compared with aerobic values in treatedhearts). This stunning was associated with concordant reductions in myocardial oxygenconsumption during recovery (−15 Δ%,p≤ 0.02 for the control group, and -21 Δ%,p≤ 0.01 for the treated group).14CO2production from labeled glucose was strongly suppressed duringpreischemic perfusion in both groups, rose slightly during ischemia, and continued to rise in theoxfenicine group during reperfusion to twice the values measured in control hearts (p≤ 0.01).These responses were contrasted with data from five additional, similarly perfused hearts thatdid not receive Intralipid. Reducing fatty acids twofold In the perfusate caused no majorchanges in glucose oxidation as compared with control hearts. Tissue glycogen was detected inboth aerobic and reperfused myocardium and was unaffected by oxfenicine treatment. Thesedata confirm previous findings and do not support an argument for increased glucose oxidation. Rather, the results support the concept of competitive inhibition of glucose and/or itsintermediates by the preferred use of fatty acids.

ISSN:0009-7330    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The electrophysiological and mechanical properties of the vasodilator minoxidil sulfate (MNXS) were examined in isolated smooth muscle cells and strips from rabbit portal vein. At micromolar concentrations, MNXS inhibited norepinephrine (0.1–1.0 μM) -induced contractionsin isolated muscle strips. In isolated cells, norepinephrine caused a dose-dependentdepolarization of the resting membrane potential, which was significantly attenuated by MNXS(5 μM); MNXS alone caused a hyperpolarization of the membrane potential. This hyperpolarizationwas insensitive to Na+-K+pump blockade by ouabain, but was inhibited by the K+channel antagonist, tetraethylammonium (20 mM). In voltage-clamp experiments, a resting(background) conductance associated with the resting membrane potential was identified. Thisconductance, which previously has been shown to be reduced by Ba2+as well as tetraethylammonium, was increased by MNXS (2 μM). In additional experiments, whole-cell L-type Ca2+currents were inhibited by micromolar concentrations of MNXS. These experiments show thatconcentrations of MNXS that inhibit norepinephrine-induced contractions promote K+conductanceand inhibit Ca2+entry through voltage-dependent Ca2+channels in vascular smoothmuscle cells. These electrophysiological effects of MNXS may be responsible for the vasorelaxanteffects of the drug observed in vitro and in vivo.

ISSN:0009-7330    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

To determine if inhibition of leukocyte adhesion and aggregation could improve postischemic ventricular dysfunction (“stunning”), a monoclonal antibody (904) that binds to the adhesionpromotingMol glycoprotein on the cell surface of leukocytes was administered intravenously(0.5 mg/kg) to open-chest dogs before a 15-minute coronary occlusion. Ultrasonic crystalsplaced in ischemic and control myocardium were used to measure systolic wall thickeningduring a 15-minute occlusion of the left anterior descending artery and for 3 hours afterreperfusion. Myocardial blood flow was measured with tracer-labeled microspheres beforeocclusion, after 10 minutes of occlusion, 3 minutes of reperfusion, and at 1 and 3 hours afterreperfusion. Six animals receiving anti-Mol antibody had antibody excess demonstrated withimmunofluorescence techniques at 5 minutes and 3 hours of reperfusion; this finding'indicatedsaturation of binding sites. Five animals served as controls and received an antibody (murineimmunoglobulin G) that does not influence neutrophils. The two groups did not differhemodynamically during ischemia and reperfusion. Risk areas and myocardial blood flow werealso not significantly different between the two groups. The main parameter used to defineregional myocardial stunning, percentage systolic wall thickening in the ischemic/reperfusedarea, did not differ significantly between the two groups. Specimens from nonischemicmyocardium were compared with ischemic specimens for myeloperoxldase content There wereno significant differences within or between groups. These data indicate that the anti-Molmonoclonal antibody (904) is not effective in improving the profound myocardial dysfunctionthat persists for 3 hours of reperfusion after IS minutes of ischemia.

ISSN:0009-7330    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

To evaluate long-term effects of contractile and mitogenic stimuli on the contractile reactivity of arterial smooth muscle, we measured the incorporation of the thymidine analogue 5- bromo-2'-deoxyuridine (BrdUrd) and mechanical responses in arterial segments that had been maintained in tissue culture. The experiments were performed on renal arteries that had been isolated from adult rats, chemically sympathectomized, mechanically denuded from endothelium and mounted under distension. Exposure of arterial segments for up to 3 weeks to culture medium supplemented with fetal calf serum resulted in the following consecutive changes: a strong acute contraction, selective pharmacological changes that included decreased contractile responses to phenylephrine and vasopressin and increased relaxing responses to isoproterenol, increased incorporation of BrdUrd, a progressive fall in contractile responses to all vasoconstrictor stimuli, and an increase in excitability. Serum-free medium resulted in a much smaller acute arterial contraction, induced less incorporation of BrdUrd, accelerated the occurrence of hyperexcitability, but did not affect early pharmacological changes or the subsequent fall in overall arterial contractility with tissue culture. Dialysis of the serum or addition of ketanserin abolished the contractile effect of serum but did not affect the incorporation of BrdUrd or the loss of contractility with tissue culture. Addition of serotonin to serum-free culture medium mimicked the contractile response to serum but not the stimulation of BrdUrd incorporation. These data indicate that tissue culture alters the properties of the arterial wall, that contraction does not underlie the proliferative response of arterial smooth muscle to serum-derived mitogens in vitro, and that stimulation of DNA synthesis does in itself not lead to selective changes in arterial contractility.

ISSN:0009-7330    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Three different isoforms of the inhibitory guanine nucleotide-binding protein α-subunit (GIα) have been cloned. However, little information on the cardiac-specific expression of these isoforms is available. The deduced amino acid sequence of a full-length GIα2 complementary DNA from a canine ventricular library displays several unique residues compared with those from other species. In contrast to previously described complementary DNA clones for GIα2 this complementary DNA has a complete 3'-untranslated region with the expected consensus sequence for polyadenylation. GIα2 is the predominant isoform in the heart, and its message level of 14.7 ± 4.9 pg/10 μg total ventricular RNA is about fourfold lower than that of the stimulatory guanine nucleotide-binding protein.

ISSN:0009-7330    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

We measured Ca2+uptake by sarcoplasmic reticulum prepared from left ventricular myocardium obtained from six nonfailing human hearts and nine excised hearts from patients with class IV idiopathic dilated cardiomyopathy. Ca2+uptake had a Vmaxof 593 ± 82 nmol/mg-min, a K0.5of 0.68 ± 0.07 μM, and an nHILLof 1.7 ± 0.1 in the nonfailing hearts. The corresponding values in the excised failing hearts were 593 ± 36 nmol/mg-min, 0.63 ± 0.03 μM, and 1.6 ± 0.1. The β-receptor density in crude sarcolemma prepared from left ventricular myocardium was 110.0 ± 15.3 fmol/mg in the unmatched donors and 52.1 ± 4.5 fmol/mg in the excised failing hearts. These results suggest that abnormal Ca2+handling in idiopathic dilated cardiomyopathy in humans is not the result of any intrinsic alteration of Ca2+uptake by sarcoplasmic reticulum.

ISSN:0009-7330    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The effect of 1 hour of myocardial ischemia on the function of the stimulatory guaninenucleotide- binding protein G1was examined. This study follows our recent finding that myocardial ischemia increases the density of β-adrenoreceptors in a conscious canine model while having the opposite effect on the activity of adenylate cyclase. Coronary artery occlusion was induced in five conscious dogs and verified by measurement of blood flow using the Doppler and microsphere techniques. Alterations in the level and function of G1were examined in sarcolemmal membranes prepared from ischemic and nonischemic regions of the left ventricle. After 1 hour of coronary artery occlusion, the functional activity of sarcolemmal G1, as determined by reconstitution with eye" membranes, decreased by 27 ± 7% in the ischemic zone. Cholera toxin labeling performed in parallel with the reconstitution studies demonstrated a similar decrease of 28 ± 7%. This was associated with decreases in basal activity and decreases in adenylate cyclase activity stimulated by GTP, GTP phis isoproterenol, sodium fluoride, and forskoBn. Thus, a delect distal to the β-adrenoreceptor occurs in the transduction of adrenergjc signals to the heart as a consequence of 1 hour of ischemia.

ISSN:0009-7330    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The mechanism of propranolol-inhibited sarcolemmal membrane lipid peroxidation was investigated by electron spin resonance spin-trapping technique using 5,5-dimethyl- 1-pyrroline-N-oxide (DMPO) and 2-methyl-2-nitrosopropane (MNP). Highly purified canine myocytic sarcolemma were peroxidized by a superoxidc-driven (from dihydroxyfumarate) and Fe3+-catalyzed free radical-generating system. Hydroxyl radicals (-OH), identified by electron spin resonance signals as DMPO-OH adducts, were generated in the aqueous phase. Propranolol up to 500 μM did not effectively reduce the intensity of the DMPO-OH adducts. When the sarcolemma were incubated with MNP before the addition of free radicals, MNP adducts characteristic of carbon-centered radicals were produced. Pretreatment of the membranes with propranolol (3-100 μM) decreased the intensity of the MNP adducts in a log concentrationdependent manner; the EC50is about 7 μM. D- and L-propranolol were found equally effective. When protein-depleted sarcolemmal lipids were similarly incubated with MNP and the free radical system, identical MNP adducts were observed; this finding suggests that the adducts were lipid-derived products arising from lipid peroxidation. Furthermore, their formation was also inhibited by propranolol pretreatment. Since propranolol is not an effective scavenger of oxygen radicals in the aqueous phase, the data suggest that the antiperoxidative effect of propranolol is due to its lipophilic interaction with the membrane and thus subsequent interruption of the free radical chain reactions.

ISSN:0009-7330    

出版商:OVID    

年代:1989

数据来源: OVID