Biomedical subjects

M Karmazyn

Publications and source records attributed to M Karmazyn.

At least 91 records · Page 5Linked to original sources

PubMed1989

A direct role of endogenous prostaglandins in reperfusion-induced cardiac arrhythmias.

The possible role of prostaglandins (PG) in arrhythmias associated with ischemia and reperfusion was studied in isolated, superfused canine Purkinje tissues. Ischemic conditions caused partial depolarization and decrease of excitability. Neither inhibition of PG synthesis (ibuprofen, 30 micrograms/mL) nor addition of exogenous PGF2 alpha (1 ng/mL) modified responses to "ischemia." Reperfusion with normal Tyrode's solution stimulated PG production (measured as 6-keto-PGF1 alpha) and induced a series of electrophysiological events. Under control conditions, Purkinje fibres rapidly repolarized. Subsequently, these tissues began to depolarize and oscillatory afterpotentials appeared. Purkinje tissues depolarized further and became temporarily inexcitable. Return of activity was associated with depolarization-induced automaticity. Ibuprofen prevented reperfusion-stimulated PG release. Ibuprofen also increased the magnitude of early repolarization and greatly attenuated subsequent depolarization. Depolarization-induced automaticity was not observed under these conditions; however, oscillatory afterpotentials were not abolished by ibuprofen. Addition of PGF2 alpha to "ischemic" and reperfusion solutions in the presence of ibuprofen restored the arrhythmogenic responses. We conclude that release of endogenous prostaglandins contributes to electrophysiological changes elicited by reperfusion in canine Purkinje fibres.

Animals↗

PubMed1989

Synthesis and relevance of cardiac eicosanoids with particular emphasis on ischemia and reperfusion.

Eicosanoids represent a family of compounds derived primarily from arachidonic acid. It is now known that arachidonic acid can undergo metabolism via at least three distinct pathways, although the most readily understood are those resulting in prostaglandin or leukotriene formation via cyclooxygenase and 5-lipoxygenase, respectively. These products can be synthesized by the heart or can be released from accumulating neutrophils under various pathological conditions. Eicosanoids possess a wide array of pharmacological actions that could be of importance either in the initiation or modulation of various cardiac diseases. Here, we review the potential importance of eicosanoids to ischemic heart disease. Data are cited that examine the potential importance of these compounds to experimentally induced cardiac injury as well as clinically observed ischemic heart disease. Particular emphasis is placed on recent studies that document the relevance of endogenously synthesized arachidonic acid metabolites as well as the consequence of modulating eicosanoid synthesis through pharmacological or dietary means on cardiac injury under experimental or clinical situations.

Coronary Disease↗

PubMed1989

A rapid phosphate-induced depression of heart subsarcolemmal mitochondrial oxidative phosphorylation.

Inorganic phosphate (Pi) was added to suspensions of interfibrillar (IFM) and subsarcolemmal (SLM) mitochondria. With 20 mM Pi, significant depression in SLM oxidative phosphorylation was seen after 60 seconds exposure whereas 120 seconds was required to depress IFM, although to a lesser degree. Oxidative phosphorylation rate of SLM was significantly depressed by 1 minute incubation with 2.5-20 mM Pi, whereas IFM were unaffected. Five minute incubation with similar Pi concentrations produced equal depression in both populations. We postulate that the rapid increase in intracellular Pi may contribute to contractile failure associated with early ischemia by depressing a critical pool of ATP synthesis represented by SLM.

Animals↗

PubMed1988

Differential utilization of long chain fatty acids during triacylglycerol depletion. I. Rat heart after ischemic perfusion.

Rat hearts were perfused with Krebs-Henseleit buffer for 90 min according to the Langendorff procedure. Normoxic perfusion for 90 min resulted in minor changes in fatty acid composition and a decrease in residual heart triacylglycerol to 60% of preperfusion values. When the protocol included 30 min of slow perfusion-induced ischemia, the hearts were observed to be depleted of 89% of their initial triacylglycerol content. The triacylglycerol fatty acid composition (mg %) remained similar after compared to before perfusion except for a 121 mg % increase in stearic acid and a 225 mg % increase in arachidonic acid. The percentage composition of both fatty acids was significantly inversely correlated with the amount of triacylglycerol remaining in the heart after perfusion. Postperfusion, arachidonic acid and stearic acids were present at nearly 1:1 in the residual heart triacylglycerol, suggesting that a common mechanism may be involved in the selective retention of these fatty acids by the heart.

Animals↗

PubMed1988

Copper intake affects rat heart performance during ischemia-reperfusion: possible relation to altered lipid and fatty acid metabolism.

Hearts from rats fed low copper (1.3 mg copper/kg diet) or a copper-supplemented diet (243 mg copper/kg diet) were perfused for 90 min according to the Langendorff method. The perfusion protocol included 30 min normoxia, 30 min ischemia and 30 min reperfusion. After 90 min perfusion, hearts from the low copper group had gained more weight, had lower coronary perfusion pressure, developed less force of contraction and secreted less 6-keto PGF1 alpha into the perfusate than hearts from the copper-supplemented group. After perfusion, the major lipid change in the hearts from both groups was a 85-90% decrease in total triacylglycerol. In both groups, stearic acid and arachidonic acid (mg%) were increased in the triacylglycerol fraction after heart perfusion. The quantitative (mg/g) decrease in the triacylglycerol content of stearic acid and arachidonic acid was significantly less in the copper-supplemented group. After perfusion, dihomo-gamma-linolenic acid (mg/g) was lower in heart phospholipids from the low copper group. Dihomo-gamma-linolenic/arachidonic acid (microgram/mg) was significantly decreased after perfusion only in the hearts from the low copper group. Lipid and fatty acid changes in the hearts of the rats fed low dietary copper may contribute to abnormal heart function in this group.

Animals↗

PubMed1988

Amiloride enhances postischemic ventricular recovery: possible role of Na+-H+ exchange.

Amiloride (40 micrograms/ml) was studied in the isolated rat heart subjected to low-flow ischemia followed by reperfusion. Reperfusion after 30 min of ischemia produced recoveries of force, rate of force development (+dF/dt), and rate of relaxation (-dF/dt) of 42, 82, and 71%, respectively, in control hearts. Amiloride did not enhance the maximum degree of recovery, although, when present during ischemia, it markedly shortened the time required for peak recovery. Reperfusion after 60 min of ischemia resulted in 18, 43, and 34% recovery of force, +dF/dt, and -dF/dt, respectively. Amiloride significantly enhanced recovery to a maximum of 39, 88, and 78% for force, +dF/dt, and -dF/dt, respectively. The improved contractile recovery was accompanied with substantial reductions in the release of creatine kinase (CK) and 6-ketoprostaglandin F1 alpha. Coronary perfusion pressure and resting tension were generally unaffected by amiloride, although there was a moderate tendency to attenuate these parameters after reperfusion. The salutary effects of amiloride were dependent on the drug's presence during ischemia with maximum protection when it was administered during both ischemia and reperfusion and no benefit when added at the time of reperfusion. Because of amiloride's well-documented property in inhibiting Na+-H+ exchange, it is possible that this process plays an important role in modulating the cardiac response to reperfusion.

Amiloride↗

PubMed1988

Heat-shock response is associated with enhanced postischemic ventricular recovery.

In cells, hyperthermia induces synthesis of heat-shock proteins and the acquisition of thermotolerance. Thermotolerant cells are resistant to subsequent oxidative stress. In this study, heat-shocked hearts were examined for evidence of protection during ischemia and reperfusion. Rats were exposed to 15 minutes of 42 degrees C hyperthermia. Twenty-four hours later their hearts were isolated and perfused and the contractility examined during and after ischemic perfusion. No protection was observed during ischemic perfusion. However, upon reperfusion heat-shocked hearts had recovery of contractility within 5 minutes of reperfusion, while control hearts showed no contractility at this time. Throughout 30 minutes of reperfusion heat-shocked hearts had significantly improved recovery of contractile force, rate of contraction and rate of relaxation. Creatine kinase release, associated with reperfusion injury, was significantly reduced from a high of 386.8 +/- 78.9 mU/min/g heart wt for controls to 123.7 +/- 82.9 mU/min/g heart wt for heat-shocked hearts at 5 minutes of reperfusion. Following 30 minutes of reperfusion, ultrastructural examination revealed less damage of mitochondrial membranes in the heat-shocked hearts. Further biochemical investigations revealed that the antioxidative enzyme, catalase, was significantly increased to 137 +/- 12.7 U/mg protein in the heat-shocked hearts while the control value was 64.8 +/- 8.3 U/mg protein. Hyperthermic treatment, which induces the heat-shock response, may be therapeutic for salvaging ischemic myocardium during reperfusion, through a mechanism involving increased levels of myocardial catalase.

Animals↗

PubMed1987

Role of prostaglandins in the arrhythmogenic effects of ouabain on isolated guinea pig hearts.

We examined the hypothesis that endogenous prostaglandins participate in the arrhythmogenic influence of ouabain in guinea pig hearts. Addition of ouabain (10 ng/ml) resulted in a 5-fold increase in the release of 6-keto-prostaglandin F1 alpha in the coronary effluent. Ten of 13 hearts studied (77%) demonstrated arrhythmic activity with a mean time to the onset of arrhythmias of approximately 35 min. The nonsteroidal antiinflammatory drugs indomethacin and acetylsalicylic acid which significantly inhibited the efflux of 6-keto-prostaglandin F1 alpha also reduced the incidence of arrhythmias to 10 of 30 hearts studied. In those hearts in which arrhythmias occurred, the time to onset was significantly increased to approximately 50 and 55 min for acetylsalicylic acid and indomethacin, respectively. In contrast, exogenous prostaglandin F2 alpha (0.1 and 1 ng/ml) and prostacyclin (0.1 and 10 ng/ml) increased the incidence of arrhythmias to 100% (10 of 10 hearts studied) and decreased the time to onset to approximately 10 min. These prostaglandin pretreatments were also able to reverse the protective actions of both acetylsalicylic acid and indomethacin. Other concentrations (10 ng/ml prostaglandin F2 alpha and 1 ng/ml prostacyclin) had no influence either on the incidence of arrhythmias or their time to onset. Prostaglandin E2 (0.1 ng/ml) produced a modest but not significant decrease in the time to onset of arrhythmias although this concentration was significantly effective in reversing the nonsteroidal antiinflammatory drug effects. The inotropic, chronotropic and coronary constricting actions of ouabain were unaffected either by nonsteroidal antiinflammatory drug or prostaglandin pretreatment. These studies suggest that prostaglandins are involved, at least in part, in the arrhythmogenic actions of ouabain in the isolated guinea pig heart.

6-Ketoprostaglandin F1 alpha↗

PubMed1987

Calcium paradox-evoked release of prostacyclin and immunoreactive leukotriene C4 from rat and guinea-pig hearts. Evidence that endogenous prostaglandins inhibit leukotriene biosynthesis.

The purpose of this study was to assess the influence of the calcium paradox (5 min calcium-free perfusion followed by 15 min calcium repletion) on the release of immunoreactive leukotriene C4 and 6 Keto-prostaglandin F1 alpha from rat and guinea-pig hearts. Under control conditions or during the 5 min calcium-free perfusion period no immunoreactive leukotriene C4 was detectable in the coronary effluent. Following reperfusion with calcium-containing medium a large release of leukotriene C4 was observed although the amount was significantly greater in the rat heart. 6 keto-prostaglandin F1 alpha was detected during normal and calcium-free perfusion and the release was significantly stimulated during calcium repletion. Treatment with ibuprofen, a cyclo-oxygenase inhibitor, prevented the release of 6 keto-prostaglandin F1 alpha but increased the efflux of immunoreactive LTC4 during calcium repletion. Arachidonic acid, the substrate for prostaglandin and leukotriene synthesis increased the efflux of 6 keto-prostaglandin F1 alpha but decreased the release of leukotriene C4. The latter effect was reversed by perfusion with ibuprofen, and mimicked by prostacyclin, the primary cardiac prostaglandin. This study shows that the calcium paradox is a potent stimulus for eicosanoid release from rat and guinea-pig hearts, a phenomenon likely due to the activation of calcium-dependent enzymes. The study also suggests that endogenous prostaglandins inhibit leukotriene synthesis in cardiac tissue.

6-Ketoprostaglandin F1 alpha↗

PubMed1987

Effects of dietary cod liver oil on fatty-acid composition and calcium transport in isolated adult rat ventricular myocytes and on the response of isolated hearts to ischemia and reperfusion.

Three-week-old male and female rats were placed either on standard rat chow or chow supplemented with 10% cod liver oil for 12 weeks. Animals fed cod liver oil demonstrated reduced body weights. Cod liver oil feeding produced a significant reduction in the ratio of (n - 6)/(n - 3) fatty acids in phospholipids of the isolated myocytes. The primary changes included a significant decrease in arachidonic acid (20:4, n - 6) and elevations in eicosapentaenoic acid (20:5, n - 3) and docosahexaenoic acid (22:6, n - 3). Furthermore, isolated myocytes from cod liver oil fed rats exhibited an enhanced 45Ca2+ uptake, although 45Ca2+ release was unaffected. Dietary cod liver oil had little effect on cardiac response to ischemia and reperfusion. Thus, neither developed force or resting tension was significantly affected by diet, although the latter tended to be elevated in hearts from cod liver oil fed animals. Release of creatine kinase was unaltered by diet. The release of 6-ketoprostaglandin F1 alpha from isolated hearts was significantly reduced by dietary cod liver oil, likely due to the reduced levels of arachidonic acid. Our study indicates that dietary cod liver oil and subsequent changes in phospholipid fatty-acid content are accompanied by changes in Ca2+ transport in isolated cardiac myocytes. However, this diet produces little effect on the cardiac response to acute ischemia and reperfusion.

6-Ketoprostaglandin F1 alpha↗

PubMed1987

Injury to rat hearts produced by an exogenous free radical generating system. Study into the role of arachidonic acid and eicosanoids.

This study was designed to evaluate the effect of an exogenous free radical generating system consisting of purine plus xanthine oxidase on the isolated rat heart and in particular to assess the possible contribution of arachidonic acid or its metabolites to toxicity produced by this drug combination. Purine plus xanthine oxidase produced a time-dependent depression in cardiac contractility which was associated with stimulated release of lactate dehydrogenase (LDH). Electron microscopic analysis revealed a distinct separation of the glycocalyx from the sarcolemmal membrane with no apparent intracellular defects. Purine plus xanthine oxidase was a potent stimulus for 6-keto-prostaglandin F1 alpha (6K-PGF1 alpha) synthesis but leukotriene production was undetectable under any condition. Eicosatetraynoic acid, which totally prevents the metabolism of arachidonic acid, accelerated the loss in force and increased LDH release invoked by purine plus xanthine oxidase, but produced no noticeable change in sarcolemmal ultrastructure. Cyclooxygenase inhibitors produced little influence although pretreatment with either acetylsalicylic acid or ibuprofen decreased contractility toward the end of purine plus xanthine oxidase perfusion. Nordihydroguarietic acid, a purported inhibitor of 5'-lipoxygenase accelerated the loss in force produced by purine plus xanthine oxidase. The nordihydroguarietic acid effects were associated with reduced 6K-PGF1 alpha efflux but LDH release was unaffected. We also examined whether modification of arachidonic acid release through changes in calcium concentration was associated with altered response to purine plus xanthine oxidase. Lowering the calcium concentration to 0.41 mM (from 1.25 mM control) reduced markedly 6K-PGF1 alpha, efflux as well as LDH release. Although the latter is suggestive of protection, hypocalcemic perfusion resulted in a greater loss in force due to free radical generation. Furthermore, cells from these hearts exhibited a greater degree of glycocalyx separation. Increasing the calcium concentration to 2.50 mM produced no further toxic manifestations in the response to purine plus xanthine oxidase, although the release of 6K-PGF1 alpha was increased. Our results suggest complex toxicity induced by an exogenously generated free radical system. The injury produced by this method is restricted to sarcolemmal changes, the latter being dependent on the external calcium concentration. The study further suggests that accumulation of intracellular unesterified arachidonic acid, which may result from peroxidation of membrane lipids, increases tissue injury caused by exogenous free radicals.

5,8,11,14-Eicosatetraynoic Acid↗

PubMed1986

Activation of suppressor cells by low molecular weight factors secreted by spleen cells of tumor-bearing mice: modulatory role of prostaglandins.

We have shown previously that the spleens of mice bearing large M-1 fibrosarcomas contain inducer cells which secrete dialysable factors which activate suppressor T cells from unprimed, normal precursor spleen cells. Once activated, the suppressor cells inhibit the in vitro antibody synthesis of cocultured syngeneic splenocytes stimulated by T cell dependent antigens. In this paper we have examined the possibility that prostaglandins are involved in the activation process. Inducer and precursor cells were cultured in Marbrook vessels in chambers separated by dialysis membranes. Using this procedure, suppressor cells were activated following 12 h of culture but were not detectable after 6 h. The cyclooxygenase inhibitors, indomethacin, acetyl salicylic acid (ASA), and ibuprofen all prevented the activation of suppressor cells in a dose dependent manner. Prostaglandin (PG) E1, but not PGF2a or PGD2, restored the activation of suppressor cells in cultures containing the cyclooxygenase inhibitors. Restoration of suppressor cell activation was seen with 1 X 10(-7) M PGE1 but no activation of suppressor cells was seen in control cultures containing up to 1 X 10(-5) M PGE1. In addition, cultured spleen cells from tumor-bearing mice did not secrete higher quantities of PGE than did cells from age and sex matched normal mice. These data suggest that PGE has a modulatory rather than a direct role in the activation of suppressor cells by inducer factors from tumor-activated inducer cells.

Alprostadil↗

PubMed1986

Contribution of prostaglandins to reperfusion-induced ventricular failure in isolated rat hearts.

This study was carried out to investigate the possible contribution of endogenous prostaglandin (PG) production to failure of contractile recovery following reperfusion of hypoperfused isolated rat hearts. A 90% reduction in coronary flow rate for 60 min resulted in a time-dependent depression of contractile force and an elevation in resting tension. Reperfusion produced a slight (approximately 11%) recovery of contractile force, whereas resting tension remained elevated. Reperfusion was a potent stimulus for PG (as assessed by 6 keto-PGF1 alpha) release and resulted in levels that were significantly higher than those observed prior to ischemia. When PG synthesis was inhibited by the nonsteroidal anti-inflammatory drugs ibuprofen, indomethacin, or acetylsalicylic acid (ASA), recovery of ventricular contractility on reperfusion was significantly higher than that seen in the absence of drugs. Ibuprofen was the most effective, producing an average recovery of 70% (P less than 0.05 from control). Indomethacin and ASA produced approximately a 40% (P less than 0.05) and 35% (P less than 0.05) recovery of contractile force, respectively. The improved recovery in contractility was significantly depressed by the addition of low concentrations of prostacyclin (PGI2) and PGF2 alpha, whereas PGE2 and 6 keto-PGF1 alpha, the hydrolysis product of PGI2, were ineffective. The effects on resting tension were inconsistent. PG release during reperfusion was unrelated either to the length of the initial period of reduced coronary flow or the degree of contractile recovery; it was attenuated either by a reduction in or by an elevation of Ca concentration. These results indicate that endogenous PGs mediate, at least in part, reperfusion-associated failure of ventricular function.

6-Ketoprostaglandin F1 alpha↗

PubMed1986

Prostaglandins stimulate calcium-linked changes in heart mitochondrial respiration.

This study was done to determine the influence of prostaglandins (PGs) on oxidative phosphorylation and Ca-related changes in cardiac mitochondria. For most of the experiments mitochondria were isolated by using a nagarse-homogenization combination method that yields both subsarcolemmal and interfibrillar populations. When Ca (30-420 microM) was added a progressive stimulation in resting respiration was observed. Similarly, preaddition of Ca inhibited subsequent oxidative phosphorylation when ADP was added to the same preparation. The effect of calcium was enhanced by pretreating mitochondria with PGs E2, F2 alpha, and I2 (prostacyclin). Three PG concentrations, 100 pg/ml, 1 ng/ml, and 10 ng/ml were evaluated. For the most part the effect of PGs was concentration dependent with the exception of PGE2, which showed no effect at the highest concentration. The effects of PGs were observed when both NADH (pyruvate-malate) and succinate-linked respiratory substrates were used. Similar effects were evident when mitochondria were harvested using a non-nagarse homogenization method that yields a primarily subsarcolemmal population, although this preparation exhibited substantially higher sensitivity to Ca. None of the PGs had any direct effect on either resting respiration rate or oxidative phosphorylation in the absence of Ca, irrespective of isolation procedure or choice of substrate. The study demonstrates that PGs can augment Ca-related changes in cardiac mitochondrial respiration through an as yet unknown mechanism. The results may be important in understanding the role of endogenously synthesized PGs in cardiac pathology associated with defective intracellular Ca homeostasis.

Animals↗

PubMed1986

A possible role for endogenous prostaglandins in the electrophysiological effects of acetylstrophanthidin on isolated canine ventricular tissues.

A possible role for endogenous prostaglandins in the toxic electrophysiological effects of the aglycone acetylstrophanthidin was studied in isolated canine Purkinje fiber papillary muscle preparations by standard microelectrode techniques. Acetylstrophanthidin (5 X 10(-8) g/ml) caused a significant increase in 6-keto-prostaglandin F1 alpha release from these preparations. A significant loss of membrane potential and the development of oscillatory afterpotentials was observed, as well. Administration of either of two nonsteroidal antiinflammatory agents, indomethacin (3 X 10(-5) g/ml) or aspirin (5 X 10(-5) g/ml), in the presence of acetylstrophanthidin, abolished the stimulation of 6-keto-prostaglandin F1 alpha release and delayed and attenuated the loss of membrane potential and the development of oscillatory afterpotentials. In addition, indomethacin and aspirin appeared to preserve the electrogenic pumping capacity of Purkinje fiber cells exposed to acetylstrophanthidin. Exposure of Purkinje tissues to acetylstrophanthidin inhibited post-pacing hyperpolarization normally exhibited by these tissues. Both indomethacin and aspirin decreased this inhibition. Addition of prostacyclin (1 ng/ml) after 30 minutes of exposure to acetylstrophanthidin to preparations in which endogenous prostaglandin synthesis had been inhibited, resulted in a significant increase in the amplitude of oscillatory afterpotentials within 2 minutes. These results suggest that the presence of endogenous prostaglandins may play a role in the development of the toxic electrophysiological effects associated with acetylstrophanthidin.

6-Ketoprostaglandin F1 alpha↗

PubMed1985

Toxic properties of arachidonic acid on normal, ischemic and reperfused hearts. Indirect evidence for free radical involvement.

We studied the effect of arachidonic acid on function and CPK release of normal, ischemic and reperfused isolated rat hearts. Under control conditions arachidonate (10 micrograms/ml) produced a transient inotropic effect which gradually reversed during a 90 minute perfusion. Creatinephosphokinase (CPK) release was augmented by arachidonic acid, particularly under high flow (pre-ischemia and reperfusion) conditions. Recovery of contractility following reperfusion of ischemic myocardium was significantly depressed by arachidonic acid. Vitamin E (100 ng/ml) an antioxidant and free radical scavenger, reduced the enzyme leakage and enhanced recovery of contractility of reperfused myocardium. It also prevented the depression in contractility during control perfusion. Similar protective effects were observed by perfusing the heart with reduced calcium but not by nifedipine; a calcium channel blocker, indomethacin; a prostaglandin synthesis inhibitor or nordihydroguarietic acid; a lipoxygenase inhibitor. Arachidonic acid also inhibited membrane Na+/K+-ATPase although it is unlikely that this property mediated its cardiotoxic influence since it was not prevented by vitamin E. In addition, we observed that arachidonic acid increased the coronary resistance of isolated hearts, probably through enhanced calcium influx as this constriction was reduced by low calcium as well as by nifedipine. Thus, arachidonic acid possesses distinct properties. Its cardiotoxic influence is likely mediated by free radical generation.

Animals↗

PubMed1985

Prostaglandin involvement in hypersensitivity of ischemic hearts to arrhythmogenic influence of ouabain.

Arrhythmias were produced by ouabain (2.7 X 10(-7) M) in isolated perfused guinea pig hearts. In control hearts the average time to onset of arrhythmias following exposure to ouabain was approximately 35 min. Ligation of the left anterior descending coronary artery significantly shortened the time to arrhythmias to about 15 min. This effect of ligation was attenuated significantly by pretreating the hearts with acetylsalicylic acid (ASA) and other nonsteroidal anti-inflammatory drugs. In contrast, the protective influence of ASA was reversed by either prostaglandin (PG) E2, PGF2 alpha, or PGI2 (2.8 X 10(-9) M). When PGE2 or PGI2 were present in the absence of ASA, the time to arrhythmias following ouabain administration was significantly shortened. PGF2 alpha had no effect in these experiments. The sensitivity was enhanced significantly by treatment with arachidonic acid. This effect was reduced by treatment with ASA or indomethacin. Prostaglandin production during the experiments was estimated by monitoring release of 6-keto-PGF1 alpha, the hydrolysis product of prostacyclin. Abbreviation of time to arrhythmias by ligation was greatest in hearts that released large amounts of 6-keto-PGF1 alpha and least in those that released low amounts. These results suggest that coronary ligation potentiates the arrhythmogenic effects of ouabain by a mechanism probably mediated by prostaglandin(s).

6-Ketoprostaglandin F1 alpha↗

PubMed1985

A role for prostaglandins in reperfusion-induced myocardial injury?

Restoration of flow to hearts made ischemic for 60 min is known to produce accelerated tissue injury. In these studies, reperfusion produced an enhanced enzyme [creatine phosphokinase (CPK) and lactate dehydrogenase] efflux, development of contracture, and reduced mitochondrial oxidative phosphorylation. These effects were associated with prostaglandin (PG) production as measured by 6-keto-PGF1 alpha efflux from the heart. Three nonsteroidal antiinflammatory agents--indomethacin, aspirin, and mefenamic acid--that inhibit the cyclooxygenase-dependent conversion of arachidonic acid to PGs reduced most aspects of dysfunction associated with reperfusion. In addition, three glucocorticoids--cortisol, dexamethasone, and methylprednisolone--that prevent substrate availability for cyclooxygenase also significantly decreased CPK efflux, but had variable effects on other parameters. These studies suggest that endogenous PGs produced in the heart may contribute to the dysfunction associated with reperfusion of the ischemic myocardium.

6-Ketoprostaglandin F1 alpha↗