Plasma Myocardial Depressant Factor Research Articles

Opsonised immune complexes containing autoantigen and natural autoantibodies rescue peripheral blood B cells from apoptosis

Intracellular accumulation of calcium is thought to play an integral role in the progression of ischemic injury and cell death. We infused the calcium entry blocker, nitrendipine (1.5 μg/kg per min), into cats in order to investigate the importance of extracellular Ca2+ influx during hemorrhagic shock. Nitrendipine proved to be a potent hypotensive agent in sham shock cats when infused over a 4 h period (156 ± 9 to 90 ± 5 mm Hg) (P < 0.01). However, in hemorrhaged animals, nitrendipine treatment maintained the post-reinfusion MABP at a significantly higher (P < 0.01) value than untreated controls (79 ± 5 vs. 51 ± 4 mm Hg, respectively). Superior mesenteric artery flow (SMAF) for hemorrhaged animals treated with nitrendipine was significantly higher (9.8 ± 1.4 ml/min per kg) (P < 0.01) than that for untreated cats (4.2 ± 0.4 ml/min per kg), at 2 h post reinfusion. There was no significantly increase in SMAF during oligemia in the nitrendipine-treated animals. Nitrendipine was also found to significantly retard the appearance of cathepsin D in the plasma of hemorrhaged cats as well as reduce plasma proteolysis to values not significantly different from sham shock animals. Furthermore, myocardial depressant factor (MDF) activity in the plasma of nitrendipine-treated shock cats was not significantly different from sham shock animals, while the plasma MDF activity for shock cats receiving vehicle increased 3-fold (P < 0.001). The beneficial effects for nitrendipine in hemorrhagic shock are likely due to both its vasodilator function and its ability to reduce intracellular Ca2+ accumulation during ischemia, thereby reducing disruption of cell membrane systems.

Platelet activating factor interaction with tumor necrosis factor and myocardial depressant factor in splanchnic artery occlusion shock

Anaesthetized rats, subjected to total occlusion of the superior mesenteric artery and the celiac trunk for 45 min, developed a severe shock state (splanchnic artery occlusion shock) resulting in a fatal outcome within 75–90 min after release of the occlusion. Shocked rats, treated with an intravenous bolus of L-659,989, a specific platelet activating factor (PAF) receptor antagonist (12.5, 25 or 50 nmol/kg, 4 min after reperfusion followed, 8 min thereafter, by a continuous infusion of 125, 250 or 500 nmol/kg for 30 min), maintained post-release mean arterial blood pressure at significantly higher values than did rats receiving the vehicle. Treatment with L-659,989 significantly increased survival rate, blunted the rise in plasma myocardial depressant factor activity and lowered serum and macrophage levels of tumor necrosis factor (TNF-a). In addition, the drug completely restored macrophage phagocytosis, improved macrophage killing and significantly inhibited leukopenia. To investigate the interaction between PAF, TNF-a and myocardial depressant factor, the blood levels of these three mediators were evaluated: shocked rats exhibited increased PAF levels with a peak at 30 min. The plasma levels of PAF peaked earlier than did either serum TNF-a or plasma myocardial depressant factor. Both peaks occurred 75 min after the release of occlusion. The results of this study therefore suggest that PAF is a key mediator of splanchnic artery occlusion shock and plays a permissive role in inducing the release of other factors (i.e. TNF-a and myocardial depressant factor) that are relevant to shock.

Evidence for a role of nitric oxide in hypovolemic hemorrhagic shock.

Hypovolemic hemorrhagic shock was induced in rats by intermittently withdrawing blood from an iliac catheter for 20 min until mean arterial blood pressure (MAP) decreased to 30 mm Hg. Survival rate, survival time, plasma myocardial depressant factor (MDF) activity, MAP, and microscopic gastric alterations were then evaluated. NG-nitro-L-arginine methyl-ester (L-NAME), a selective inhibitor of nitric oxide (NO) production from L-arginine, was injected intravenously (i.v.) after the bleeding was discontinued. Untreated hemorrhagic shocked rats died in 27 +/- 3.3 min, had enhanced plasma activity of MDF, and exhibited hemorrhagic infiltrates in gastric fundus mucosa. L-NAME (5 and 10 mg/kg) significantly increased survival rate and time, blunted the increase in plasma MDF activity, and protected against the gastric lesions induced by hemorrhagic hypovolemic shock. All these protective effects were reversed by a bolus of L-arginine (30 mg/kg/i.v.), given 2 min after administration of L-NAME. Our findings suggest that NO production plays an important role in the pathophysiology of hemorrhagic shock.

Beneficial Effects of Transforming Growth Factor-β and Tissue Plasminogen Activator in Splanchnic Artery Occlusion and Reperfusion in Cats

We studied the effects of transforming growth factor-beta (TGF-beta), tissue plasminogen activator (tPA), and their combination in cats subjected to splanchnic artery occlusion (SAO) with reperfusion. Untreated anesthetized cats subjected to total occlusion of the celiac, superior, and inferior mesenteric arteries for 120 min, followed by reperfusion, uniformly died within 120 min after reperfusion. The mean survival time was 75 +/- 8 min. Plasma amino-nitrogen concentrations and cathepsin D and myocardial depressant factor (MDF) activities were markedly elevated following reperfusion. Superior mesenteric artery (SMA) rings isolated from cats subjected to SAO with reperfusion exhibited a significant loss of vasorelaxation to the endothelium-dependent dilators acetylcholine and A-23187. Administration of tPA (1 mg/kg) intravenously just before reperfusion did not prolong survival time (81 +/- 10 min) nor did it influence any biochemical or cardiovascular responses following reperfusion or ameliorate the depressed endothelium-dependent relaxation of SMA rings. In contrast, TGF-beta (50 micrograms/cat) ameliorated the SAO postreperfusion state in terms of survival rate and plasma MDF activity, and protected against depressed endothelium-dependent relaxation of SMA rings. TGF-beta alone slightly increased the survival time to 102 +/- 11 min. However, combined treatment with tPA (1 mg/kg) and TGF-beta (50 micrograms/cat) preserved endothelium-dependent relaxation and prevented increases in plasma amino-nitrogen more prominently than TGF-beta given alone and significantly increased the survival time to 118 +/- 3 min (p less than 0.01). These results indicate that TGF-beta exerts beneficial effects in SAO followed by reperfusion in cats, and tPA has an augmenting action on some of the beneficial effects of TGF-beta. These findings suggest that TGF-beta alone or in combination with tPA may be potentially useful therapeutic regimens in splanchnic ischemia shock by preserving splanchnic parenchymal and endothelial cells.

Protective Effect of Cloricromene, a Coumarine Derivative, in Hypovolemic Hemorrhagic Shock in the Rat

Hypovolemic hemorrhagic shock was induced in male anesthetized rats by intermittently withdrawing blood from an iliac catheter over a period of 20 min until mean arterial pressure (MAP) fell to 30 mm Hg. Survival rate, MAP, plasma myocardial depressant factor (MDF) activity and plasma levels of both TxB2 and 6-keto PGF1 alpha were then evaluated. Cloricromene (0.5, 1, and 2 mg/kg) or an equal volume of vehicle (0.9% NaCl solution) were injected intravenously 5 min after the end of the bleeding. Hemorrhagic shocked rats showed enhanced plasma levels of MDF, TxB2 and 6-keto PGF1 alpha. All vehicle-treated rats died within 25 min. Cloricromene (1 and 2 mg/kg) given curatively significantly increased survival rate and blunted the rise in plasma MDF and TxB2. Moreover, cloricromene reversed the severe hypotension and the ST-segment elevation occurring during hemorrhagic shock. The data suggest that cloricromene exerts beneficial effects in experimental hypovolemic shock, probably reversing myocardial failure.

Effects of fructose 1,6-diphosphate on splanchnic artery occlusion shock in the rat

Splanchnic artery occlusion (SAO) shock, produced by clamping splanchnic arteries for 45 min followed by the release of occlusion, was induced in male rats, treated 15 min before surgery, with fructose 1,6-diphosphate (FDP) or with equivalent doses of fructose or inorganic phosphate. Survival rate, peritoneal macrophage phagocytosis and plasma levels of myocardial depressant factor (MDF) were measured. Shocked animals pretreated with vehicle exhibited 24.6 ± 0.9% phagocytic activity, 110 ± 3.9 units/ml MDF plasma levels and 0% survival. Sham animals showed the following values: survival 100%; phagocytosis, 49.5 ± 1.3%; MDF, 22 ± 2.9 units/ml. Pretreatment with FDP (25 mg/kg/i.v.) significantly improved survival rate (50%) and macrophage phagocytosis (37.9 ± 0.4%) and reduced plasma MDF levels (77 ± 3 units/ml). Equivalent doses of fructose and inorganic phosphate did not improve survival, as well as lower doses of FDP. These results suggest a beneficial effect of FDP in SAO shock.

Protective Effects of a Platelet Activating Factor (PAF) Antagonist and Its Combined Treatment with Prostaglandin (PG) E1 in Traumatic Shock

We have investigated the role of platelet activating factor (PAF) in the pathogenesis of a murine model of traumatic shock using CV-6209, a specific antagonist of PAF. CV-6209, at a dose of 1 mg/kg (i.v.) given after trauma, significantly improved survival rate at 150 min and overall survival time. Furthermore, the plasma accumulation of the lysosomal hydrolase, cathepsin D, and a cardiotoxic peptide, myocardial depressant factor (MDF), were also attenuated by CV-6209 in traumatic shock. Combined treatment employing low doses of CV-6209 [0.2 mg/kg, i.v. and prostaglandin (PG) E1, 0.8 microgram/kg/min] in this shock model was also examined. CV-6209 (0.2 mg/kg) or PGE1 (0.8 microgram/kg/min) alone at these doses showed only minimal effects on survival, or plasma cathepsin D or MDF activities. However, combined treatment with CV-6209 (0.2 mg/kg, i.v.) and PGE1 (0.8 microgram/kg/min) significantly improved survival rate at 150 min, overall survival time, and decreased the accumulation of plasma MDF. These results suggest that PAF may play an important pathophysiologic role in traumatic shock in rats. Moreover, combination therapy using a PAF antagonist and PGE1 may be useful for the treatment of traumatic shock.

Efficacy of a combination thromboxane receptor antagonist and lipoxygenase inhibitor in traumatic shock.

The effects of a thromboxane receptor antagonist having lipoxygenase inhibitory activity, L-655,240 (3-[1-(4-chlorobenzyl)-5-fluoro-3-methyl-indol-2-yl]2,2-dimethylpropa noic acid) (1 mg/kg per h) were studied in a standardized model of traumatic shock. Pentobarbital (35 mg/kg) anesthetized rats subjected to Noble-Collip drum trauma were characterized by a 82 +/- 12 min survival time, a 20-fold increase in plasma cathepsin D activity, and a 6-fold increase in plasma myocardial depressant factor (MDF) activity. L-655,240 significantly attenuated the accumulation of MDF activity in the plasma (74 +/- 3 vs. 46 +/- 4 units/ml), vehicle vs. drug, respectively, and significantly (P less than 0.01) prolonged survival time to 206 +/- 26 min. However, plasma cathepsin D was not significantly altered with L-655,240 administration during traumatic shock. L-655,240 at 20 micrograms/ml markedly attenuated minced rat lung fragments from producing LTC4 and LTD4.L-655,240 exhibited significant anti-proteolytic activity in pancreatic homogenates. Therefore, L-655,2340 does not stabilize lysosomal membranes directly, but exerts an anti-proteolytic action which appears to curtail the production of a myocardial depressant factor by the ischemic pancreas, thus protecting during traumatic shock. A combination anti-eicosanoid drug such as L-655,240 may therefore prove to be an important therapeutic agent in acute ischemic disorders including traumatic shock.

Anti shock psiof the prostacyclin analog, iloprost, in traumatic shock

The effects of iloprost, a synthetic carbacyclin derivative of prostacyclin (PGI 2) was studied in a standardized model of traumatic shock. Pentobarlitai anesthetized rats (33 mg/kg) subjected to Noble Collip drum trauma were characterized' by a 84 ± 10 minute survival time, a 16-fold increase in plasma cathepsin D activity, and a 5-fold increase in plasma myocardial depressant factor (MDF) activity. Iloprost significantly attenuated the accumulation of MDF activity in the plasma (69 ± 14 vs. 20 ± 6 U/ml) vehicle vs. drug (p<0.01), respectively, and significantly prolonged survival time to 243 ± 36 minutes (p<0.01). Plasma cathepsin D activity was also significantly attenuated (12 ± 1.8 vs. 6.2 ± 2.1 U/ml , vehicle vs. drug, respectively (p<0.02). Iloprost exhibited significant anti-proteolytic activity in pancreatic homogenates. Iloprost appears to exert a membrane stabilizing effect decreasing plasma cathepsin D activity and attentiating MDF production, probably secondarily to its anti-proteolytic effect and its maintenance of the splanchnic circulation. Iloprost may therefore prove to be a useful therapeutic agent in acute ischemic disorders including traumatic shock.

Left ventricular function during lethal and sublethal endotoxemia in swine.

Our previous studies suggested that after a median lethal dose (LD50) of endotoxin, cardiac contractility was depressed in nonsurviving dogs. The canine cardiovascular system is unlike humans in that dogs have a hepatic vein sphincter that is susceptible to adrenergic stimulation capable of raising hepatic and splanchnic venous pressures. We retested the hypothesis that lethality after endotoxin administration is associated with cardiac contractile depression in pigs, because the hepatic circulation in this species is similar to that of humans. We compared cardiac mechanical function of pigs administered a high dose (250 micrograms/kg) or a low dose (100 micrograms/kg) endotoxin by use of the slope of the end-systolic pressure-diameter relationship (ESPDR) as well as other measurements of cardiac performance. In all the pigs administered a high dose, ESPDR demonstrated a marked, time-dependent depression, whereas we observed no significant ESPDR changes after low endotoxin doses. The other cardiodynamic variables were uninterpretable, due to the significant changes in heart rate, end-diastolic diameter (preload), and aortic diastolic pressure (afterload). Plasma myocardial depressant factor activity accumulated in all endotoxin-administered animals, tending to be greater in the high-dose group. In this group, both subendocardial blood flow and global function were depressed, whereas pigs administered the low dose of endotoxin demonstrated slight, but nonsignificant, increases in flow and function. These observations indicate that myocardial contractile depression is associated with a lethal outcome to high doses of endotoxin. One possible mechanism for this loss of contractile function may be a relative hypoperfusion of the subendocardium.

Beneficial effects of a neutral protease inhibitor in traumatic shock

Eglin C is a polypeptide inhibitor of the neutral proteases elastase and cathepsin G. We have investigated its action in traumatic shock in rats. Eglin C (2 mg/kg) given following trauma prolonged survival time from 2.3 ± 0.5 h to 3.6 ± 0.4 h (p<0.05) in traumatized rats. Although eglin C treatment had no significant effect on the increase in plasma cathepsin D activity, eglin C administration significantly blunted plasma myocardial depressant factor (MDF) accumulation, 54 ± 3 vs 79 ± 8 U/ml (p<0.02). Our findings indicate a potential role for neutral proteases in toxic factor formation.

Salutary effects of two verapamil analogs in traumatic shock.

We studied the effects of two verapamil analogs, anipamil and ronipamil, in traumatic shock. Noble-Collip drum trauma produced a shock state characterized by an eight-fold increase in plasma cathepsin D activity, a 13-fold increase in the rate of plasma myocardial depressant factor (MDF) accumulation, and a survival time of 1.9 ± 0.1 hours. Neither verapamil analog had any significant effect on attenuating the shock-induced rise in plasma cathepsin D activity. However, both anipamil and ronipamil (p < 0.01) significantly blunted the rate of MDF accumulation in the plasma. In addition, these agents significantly inhibited proteolysis in vitro. Both analogs significantly prolonged survival time to 3.1 ± 0.6 h at 0.25 mg/kg (p < 0.05) and to 4.4 ± 0.3 h at 1.0 mg/kg (p < 0.001). Anipamil appears to provide a more potent protection in this shock model; however, both verapamil derivatives possess promising anti-shock potential.

Inhibitors of lipoxygenase products improve survival in traumatic shock

We have used three selective inhibitors of arachidonic acid metabolism in order to investigate the role of lipoxygenase metabolites in the pathogenesis of traumatic shock (LD 90). The following inhibitors were used: CGS-5391B (2.5 mg/kg), a cyclooxygenase and lipoxygenase inhibitor, CGS-5677 (2.0 mg/kg), a selective lipoxygenase inhibitor, and U-60, 257 (0.3 mg/kg), a putative inhibitor of glutathione-s-transferase. These inhibitors did not alter arterial blood pressure or heart rate when given to sham shock rats. The traumatic shock model was characterized by a 4.5-fold increase in plasma cathepsin D activity, a 4-fold increase in plasma myocardial depressant factor (MDF) activity, and a mean survival time of 1.5 ± 0.2 h. Only the dual inhibitor significantly blunted the accumulation of cathepsin D in the plasma (7.5 ± 0.8 vs 11.3 ± 0.8 U/ml, p<0.01). However, all three inhibitors significantly suppressed plasma MDF accumulation by 50–60%: CGS-5391B, CGS-5677, and U-60,2257 (p<0.01). Moreover, these three agents significantly improved survival time in traumatic shock. The increased survival time and reduced MDF activity afforded by these inhibitors suggest a significant role for lipoxygenase metabolites, particularly LTC 4 and LTD 4, in the pathogenesis of traumatic shock.

Beneficial effect of anisodamine in hemorrhagic shock.

Anisodamine , an alkaloid extracted from Anisodus tanguticus , is widely used in China in the treatment of septic shock, but its mechanism of action is unknown. We studied its antishock action in cats in a well controlled model of hemorrhagic shock. A bolus dose of 1 mg/kg was given intravenously 20 min after MABP was stabilized at 40-45 mm Hg, followed by i.v. infusion of 2 mg/kg/h during the oligemic period. Two hours post-reinfusion, MABP was significantly higher (106 +/- 10 mm Hg) in the drug-treated group than in shock cats receiving only vehicle (53 +/- 6 mm Hg, P less than 0.001). Anisodamine treated shock cats exhibited significantly lower cathepsin D activity (P less than 0.02) and amino-nitrogen concentration (P less than 0.001) than untreated shock animals. Plasma myocardial depressant factor (MDF) activity was significantly increased in the untreated shock cats (61 +/- 6 Units/ml), but the plasma accumulation of MDF was significantly blunted by anisodamine (32 +/- 5 Units/ml, P less than 0.01). Anisodamine did not increase superior mesenteric artery flow ( SMAF ) in this model of hemorrhagic shock as there was no significant difference in SMAF between the two shocked groups. Thus, the beneficial effect of anisodamine probably is not due to vasodilation of the splanchnic vasculature. In vitro analysis indicates that the drug has a direct anti-proteolytic action in cat pancreatic homogenates. This may partly explain the mechanism of its action, which appears to be complex.

Salutary effects of nitrendipine, a new calcium entry blocker, in hemorrhagic shock

Intracellular accumulation of calcium is thought to play an integral role in the progression of ischemic injury and cell death. We infused the calcium entry blocker, nitrendipine (1.5 μg/kg per min), into cats in order to investigate the importance of extracellular Ca 2+ influx during hemorrhagic shock. Nitrendipine proved to be a potent hypotensive agent in sham shock cats when infused over a 4 h period (156 ± 9 to 90 ± 5 mm Hg) (P < 0.01). However, in hemorrhaged animals, nitrendipine treatment maintained the post-reinfusion MABP at a significantly higher (P < 0.01) value than untreated controls (79 ± 5 vs. 51 ± 4 mm Hg, respectively). Superior mesenteric artery flow (SMAF) for hemorrhaged animals treated with nitrendipine was significantly higher (9.8 ± 1.4 ml/min per kg) (P < 0.01) than that for untreated cats (4.2 ± 0.4 ml/min per kg), at 2 h post reinfusion. There was no significantly increase in SMAF during oligemia in the nitrendipine-treated animals. Nitrendipine was also found to significantly retard the appearance of cathepsin D in the plasma of hemorrhaged cats as well as reduce plasma proteolysis to values not significantly different from sham shock animals. Furthermore, myocardial depressant factor (MDF) activity in the plasma of nitrendipine-treated shock cats was not significantly different from sham shock animals, while the plasma MDF activity for shock cats receiving vehicle increased 3-fold (P < 0.001). The beneficial effects for nitrendipine in hemorrhagic shock are likely due to both its vasodilator function and its ability to reduce intracellular Ca 2+ accumulation during ischemia, thereby reducing disruption of cell membrane systems.

Beneficial action of a new opiate antagonist (Win 44,441-3) in hemorrhagic shock

The new opiate antagonist Win 44,441-3 (−)-isomer was infused intravenously in cats at a rate of 2 mg·kg −1·h − to determine its effect in hemorrhagic shock. Hemorrhaged cats treated with Win 44,441-3 maintained post reinfusion mean arterial blood pressure (MABP) at a higher value compared to cats receiving only the vehicle. Final MABP was 70±11 mm Hg for cats receiving vehicle compared to 103±7 mm Hg for cats receiving Win 44,441-3. These values represent 60±9% and 85±6% of initial MABP for the vehicle- and Win 44,441-3-treated cats respectively. Win 44,441-2 (+)-isomer, the inactive steroiisomer of Win 44,441-3, was also infused at 2 mg·kg −·h −1 in cats subjected to hemorrhagic shock. The final pressure in this group was 72±8 mm Hg which is 61±8% of the initial pressure for this group. Win 44,441-3 and Win 44,441-2 were both ineffective in moderating increases in circulating lysosomal hydrolase activity in shocked cats. Neither isomer stabilized lysosomal membranes or retarded proteolysis in vitro. Plasma myocardial depressant factor was significantly reduced by the opiate antagonist, Win 44,441-3 during shock. Our results show that the systemic infusion of an opiate antagonist improves the hemodynamic state of cats subjected to hemorrhagic shock while the (+)-isomer which lacks opiate antagonist activity produces no such improvement.

Protective Actions of Naloxone in Hemorrhagic Shock

The opiate antagonist, naloxone, was infused at 8 mg x kg-1 x h-1 in cats to determine its effect in hemorrhagic shock. Hemorrhaged cats treated with naloxone maintained postreinfusion mean arterial blood pressure at a higher value compared to those receiving only the vehicle. Final pressures were 77 +/- 9 mmHg for cats receiving vehicle compared to 120 +/- 6 mmHg for cats receiving naloxone. These values represent 58 +/-7 and 98 +/- 6% of initial pressures for vehicle- and naloxone-treated cats, respectively (P < 0.001). Naloxone also moderated increases in circulating lysosomal hydrolase activity (4- vs. 23-fold increase) and total plasma proteolysis (33 vs. 100% increase). Plasma myocardial depressant factor activity was also significantly reduced in naloxone-treated hemorrhaged cats compared to shock cats given 0.9% NaCl (16 +/- 3 vs. 58 +/- 4 U, respectively; P < 0.001). Studies on cat papillary muscles demonstrated that naloxone at concentrations slightly higher than estimated plasma values during shock exerted a moderate positive inotropic effect. Our results show that naloxone improved the hemodynamic and biochemical state of cats in hemorrhagic shock. Inhibition of proteolysis and stabilization of lysosomal membranes appear to be ivolved in the protective action of naloxone, along with the well-known opiate-antagonistic action of this agent.

Protective actions of naloxone in hemorrhagic shock.

The opiate antagonist, naloxone, was infused at 8 mg x kg-1 x h-1 in cats to determine its effect in hemorrhagic shock. Hemorrhaged cats treated with naloxone maintained postreinfusion mean arterial blood pressure at a higher value compared to those receiving only the vehicle. Final pressures were 77 +/- 9 mmHg for cats receiving vehicle compared to 120 +/- 6 mmHg for cats receiving naloxone. These values represent 58 +/-7 and 98 +/- 6% of initial pressures for vehicle- and naloxone-treated cats, respectively (P < 0.001). Naloxone also moderated increases in circulating lysosomal hydrolase activity (4- vs. 23-fold increase) and total plasma proteolysis (33 vs. 100% increase). Plasma myocardial depressant factor activity was also significantly reduced in naloxone-treated hemorrhaged cats compared to shock cats given 0.9% NaCl (16 +/- 3 vs. 58 +/- 4 U, respectively; P < 0.001). Studies on cat papillary muscles demonstrated that naloxone at concentrations slightly higher than estimated plasma values during shock exerted a moderate positive inotropic effect. Our results show that naloxone improved the hemodynamic and biochemical state of cats in hemorrhagic shock. Inhibition of proteolysis and stabilization of lysosomal membranes appear to be ivolved in the protective action of naloxone, along with the well-known opiate-antagonistic action of this agent.