Akiyoshi Hara

Propofol Improves Functional and Metabolic Recovery in Ischemic Reperfused Isolated Rat Hearts

Propofol attenuates mechanical dysfunction, metabolic derangement, and lipid peroxidation by exogenous administration of H2 O2 in the Langendorff rat heart.In this study, we examined the effects of propofol on mechanical and metabolic changes, as well as on lipid peroxidation induced by ischemia-reperfusion, in isolated, working rat hearts. Rat hearts (in control-modified Krebs-Henseleit bicarbonate buffer) were treated with two doses (25 micro M and 50 micro M) of propofol in an intralipid vehicle. In the first protocol, propofol was administered during the preischemic and reperfusion period, whereas in the second, it was only administered during the reperfusion period. Ischemia (15 min) decreased peak aortic pressure (PAOP), heart rate (HR), rate-pressure product (RPP), coronary flow (CF), and tissue concentrations of adenosine triphosphate (ATP) and creatine phosphate. After postischemic reperfusion (20 min), the CF and tissue concentration of ATP recovered incompletely; however, PAOP, HR, and RPP did not. Ischemia-reperfusion also increased the tissue concentration of malondialdehyde (MDA). In both protocols, both doses of propofol enhanced recovery of PAOP, HR, RPP, CF, and tissue concentration of ATP during reperfusion, and inhibited the tissue accumulation of MDA. These results indicate that propofol improves recovery of mechanical function and the energy state in ischemic reperfused isolated rat hearts, and the mechanism may involve the reduction of lipid peroxidation during postischemic reperfusion. Implications: We evaluated the possible cardioprotective effects of propofol in isolated, working rat hearts subjected to 15-min ischemia, followed by 20-min reperfusion. We observed that propofol attenuated mechanical dysfunction, metabolic derangement, and lipid peroxidation during reperfusion. This latter finding seems to be one mechanism for cardioprotective effects of propofol. (Anesth Analg 1998;86:252-8)

Propofol Attenuates Hydrogen Peroxide-induced Mechanical and Metabolic Derangements in the Isolated Rat Heart

Background Oxygen‐derived free radicals are involved in tissue damage during myocardial ischemia and reperfusion. Recent in vitro studies have demonstrated that a beneficial effect of propofol lies on its free radical scavenging properties. The current study, therefore, examined whether propofol is effective against the mechanical and metabolic damage induced by exogenously administered hydrogen peroxide in the isolated rat heart. Methods Rat hearts were perfused aerobically with Krebs‐Henseleit bicarbonate buffer at a constant flow rate according to Langendorffs technique, while being paced electrically. Hearts were studied in control Krebs‐Henseleit bicarbonate buffer, with Intralipid vehicle, with 25 micro Meter or 50 micro Meter propofol for 40 min, and with 50 micro Meter propofol for 30 min followed by Intralipid for 10 min. A similar set of hearts was treated with hydrogen peroxide for 4 min, either in the absence of or beginning 10 min after Intralipid or propofol infusion. Left ventricular pressure was recorded as an index of mechanical function. The tissue concentrations of adenosine triphosphate, adenosine diphosphate, adenosine monophosphate, and creatine phosphate were measured as indices of energy metabolism. The tissue concentration of malondialdehyde was measured to evaluate lipid peroxidation. Results Hydrogen peroxide (600 micro Meter) significantly increased the left ventricular end‐diastolic pressure, decreased the left ventricular developed pressure (i.e., it produced mechanical dysfunction), and decreased tissue concentrations of adenosine triphosphate and creatine phosphate (i.e., metabolic damage). Hydrogen peroxide also increased the tissue concentration of malondialdehyde. These mechanical and metabolic alterations induced by hydrogen peroxide were significantly attenuated by propofol (25 micro Meter or 50 micro Meter), while the increase in malondialdehyde was completely suppressed by propofol. Conclusions The current study demonstrates that in the isolated heart, propofol attenuates both mechanical and metabolic changes induced by exogenously applied hydrogen peroxide. The beneficial action of propofol is probably correlated with reduction of the hydrogen peroxide‐induced lipid peroxidation.

INVOLVEMENT OF NITRIC OXIDE IN SPINALLY MEDIATED CAPSAICIN- AND GLUTAMATE-INDUCED BEHAVIOURAL RESPONSES IN THE MOUSE *

The intrathecal (i.t.) injection of capsaicin (0.1 nmol/mouse) through a lumbar puncture elicited scratching, biting and licking responses. Pretreatment with the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) (320 nmol), by i.t. injection, resulted in a significant inhibition of the behavioural response produced by i.t. capsaicin (0.1 nmol/mouse). Similar behavioural responses were induced by i.t. injections of NMDA (0.4 nmol), kainate (0.05 nmol) or AMPA (0.05 nmol), which were all inhibited by co-administration of L-NAME (20-80 nmol). L-Arginine (600 mg/kg, i.p.) but not D-arginine (600 mg/kg, i.p.) reversed the inhibitory effect of L-NAME on capsaicin-, NMDA-, kainate- and AMPA-induced behavioural response. Scratching, biting and licking responses induced by tachykinin receptor agonists, substance P, [Sar9,Met(O2)11]substance P, neurokinin A and neurokinin B were not affected by co-administration of L-NAME (40 and 80 nmol). These results suggest that spinal nitric oxide may play a significant role in mechanisms of the behavioural response to capsaicin, probably through the release of glutamate, but not tachykinins.

Characterization of prostanoid receptors mediating contraction of the gastric fundus and ileum: studies using mice deficient in prostanoid receptors

Receptors mediating prostanoid‐induced contractions of longitudinal sections of gastric fundus and ileum were characterized by using tissues obtained from mice deficient in each type and subtype of prostanoid receptors. The fundus and ileum from mice deficient in either EP3 (EP3−/− mice), EP1 (EP1−/− mice) and FP (FP−/− mice) all showed decreased contraction to PGE2 compared to the tissues from wild‐type mice, whereas contraction of the fundus slightly increased in EP4−/− mice. 17‐phenyl‐PGE2 also showed decreased contraction of the fundus from EP3−/−, EP1−/− and FP−/− mice. Sulprostone showed decreased contraction of the fundus from EP3−/− and FP−/− mice, and decreased contraction of the ileum to this compound was seen in tissues from EP3−/−, EP1−/− and FP−/− mice. In DP−/− mice, sulprostone showed increased contraction. DI‐004 and AE‐248 caused the small but concentration‐dependent contraction of both tissues, and these contractions were abolished in tissues obtained from EP1−/− and EP3−/− mice, respectively, but not affected in other mice. Contractions of both fundus and ileum to PGF2α was absent at lower concentrations (10−9 to 10−7 M), and suppressed at higher concentrations (10−6 to 10−5 M) of the agonist in the FP−/− mice. Suppression of the contractions at the higher PGF2α concentrations was also seen in the fundus from EP3−/−, EP1−/− and TP−/− mice and in the ileum from EP3−/− and TP−/− mice. Contraction of the fundus to PGD2 was significantly enhanced in DP−/− mice, and contractions of the fundus and ileum to this PG decreased in FP−/− and EP3−/− mice. Contractions of both tissues to I‐BOP was absent at 10−9 to 10−7 M and much suppressed at higher concentrations in TP−/− mice. Slight suppression to this agonist was also observed in the tissues from EP3−/− mice. PGI2 induced small relaxation of both tissues from wild‐type mice. These relaxation reactions were much potentiated in EP3−/− mice. On the other hand, significant contraction to PGI2 was observed in both tissues obtained from IP−/− mice. These results show that contractions of the fundus and ileum induced by each prostanoid agonist are mediated by actions of this agonist on multiple types of prostanoid receptors and in some cases modified by its action on relaxant receptors.

Antinociceptive effects of neonatal capsaicin in rats with adjuvant arthritis

SummaryRats were treated with capsaicin (50 mg/kg, SC) either on the second day or on the second and third days of life. A significant attenuation of the responses to noxious stimuli was obtained in the capsaicin treated animals as measured by the hot-plate or paw pressure tests but not by the tail-flick test. Furthermore, neonatal capsaicin produced a significant reduction of response in the formalin test. Capsaicin reduced the reaction latency in rats with adjuvant arthritis as measured by the hot-plate and paw pressure tests, though capsaicin did not alter the overall time course of the response to Freunds adjuvant. Capsaicin also attenuated the weight loss or the decreased ambulatory and rearing behaviour which occurred in the control animals with adjuvant arthritis. It is suggested that neonatal treatment with capsaicin may relieve the responsiveness to longlasting nociceptive stimuli by adjuvant in rats.

Ranolazine Attenuates Palmitoyl-l-carnitine-induced Mechanical and Metabolic Derangement in the Isolated, Perfused Rat Heart

The effect of ranolazine, a novel anti‐ischaemic drug that stimulates the activity of pyruvate dehydrogenase, on palmitoyl‐l‐carnitine‐induced mechanical dysfunction and metabolic derangement in isolated perfused rat hearts has been studied and compared with the effect of dichloroacetate, an activator of pyruvate dehydrogenase. Rat hearts paced electrically were perfused aerobically at constant flow by the Langendorff technique. Palmitoyl‐l‐carnitine (4 μm) increased left ventricular end‐diastolic pressure and reduced left ventricular developed pressure (i.e. induced mechanical dysfunction); it also reduced tissue levels of adenosine triphosphate and increased tissue levels of adenosine monophosphate (i.e. induced metabolic derangement). These functional and metabolic alterations induced by palmitoyl‐l‐carnitine were attenuated by ranolazine (5, 10, and 20 μm) in a concentration‐dependent manner. In contrast, dichloroacetate (1 and 10 mm) did not attenuate palmitoyl‐l‐carnitine‐induced mechanical and metabolic derangement. In the normal (palmitoyl‐l‐carnitine‐untreated) heart, however, ranolazine did not modify mechanical function and energy metabolism.

Effects of the prostanoids on the proliferation or hypertrophy of cultured murine aortic smooth muscle cells

Effects of the prostanoids on the growth of cultured aortic vascular smooth muscle cells (VSMCs) were examined using mice lacking prostanoid receptors. Proliferation of VSMCs was assessed by measuring [3H]‐thymidine incorporation and the cell number, and their hypertrophy by [14C]‐leucine incorporation and protein content. In VSMCs from wild‐type mice, expressions of mRNAs for the EP4 and TP were most abundant, followed by those for the IP, EP3 and FP, when examined by competitive reverse transcriptase‐PCR. Those for the EP1, EP2 and DP, however, could not be detected. AE1‐329, an EP4 agonist, and cicaprost, an IP agonist, inhibited platelet derived growth factor (PDGF)‐induced proliferation of VSMCs from wild‐type mice; these inhibitory effects disappeared completely in VSMCs from EP4−/− and IP−/− mice, respectively. In accordance with these effects, AE1‐329 and cicaprost stimulated cAMP production in VSMCs from wild‐type mice, which were absent in VSMCs from EP4−/− and IP−/− mice, respectively. Effects of PGE2 on cell proliferation and adenylate cyclase were almost similar with those of AE1‐329 in VSMCs from wild‐type mice, which disappeared in VSMCs from EP4−/− mice. PGD2 inhibited PDGF‐induced proliferation of VSMCs from both wild‐type and DP−/− mice to a similar extent. This action of PGD2 was also observed in VSMCs from EP4−/− and IP−/− mice. In VSMCs from wild‐type mice, I‐BOP, a TP agonist, showed potentiation of PDGF‐induced hypertrophy. I‐BOP failed to show this action in VSMCs from TP−/− mice. The specific agonists for the EP1, EP2 or EP3, and PGF2α showed little effect on the growth of VSMCs. These results show that PGE2, PGI2 and TXA2 modulate PDGF‐induced proliferation or hypertrophy of VSMCs via the EP4, IP and TP, respectively, and that the inhibitory effect of PGD2 on PDGF‐induced proliferation is not mediated by the DP, EP4 or IP.

Effect of MET‐88, a γ‐butyrobetaine hydroxylase inhibitor, on myocardial derangements induced by hydrogen peroxide in the isolated perfused rat heart

Summary— The effect of MET‐88 (3‐(2,2,2‐trimethylhydrazinium) propionate dihydrate), a γ‐butyrobetaine (γ‐BB) hydroxylase inhibitor, on the hydrogen peroxide (H2O2)‐induced mechanical and metabolic derangements was studied in the isolated rat heart, which was perfused aerobically by the Langendorff s technique at a constant flow rate and driven electrically. In the first series of experiments, MET‐88 (100 mg/kg/d) was orally administered to rats for 10 days prior to isolation of the heart. In the second series of experiments, MET‐88 or γ‐BB was directly infused to the isolated perfused heart. In both series of experiments, H2O2 (600 μM) decreased the left ventricular developed pressure (mechanical dysfunction) and the tissue levels of high‐energy phosphates (metabolic derangement). In the first series of experiments, oral pretreatment with MET‐88 attenuated the H2O2‐induced metabolic derangement with a marked increase in the myocardial level of γ‐BB, while it did not attenuate the H2O2‐induced mechanical dysfunction. In the second series of experiments, MET‐88 (1 mM) did not attenuate the H2O2‐induced metabolic derangement, whereas γ‐BB (500 μM or 1 mM) attenuated it. Nevertheless, γ‐BB did not modify the energy metabolism of H2O2‐untreated heart (normal heart). These results suggest that oral pretreatment with MET‐88 protects the energy metabolism against the H2O2‐induced derangement and that the beneficial effect of the oral pretreatment with MET‐88 may be mediated by γ‐BB that has accumulated in the myocardium because of inhibition of γ‐BB hydroxylase.

Beneficial effect of magnesium on the isolated perfused rat heart during reperfusion after ischaemia : comparison between pre-ischaemic and post-ischaemic administration of magnesium

SummaryThe effect of high concentration of magnesium on both mechanical dysfunction and metabolic damage after ischaemia-reperfusion was studied in isolated rat hearts. The heart was perfused by the Langendorffs technique at a constant flow (10 ml/min) with modified Krebs-Henseleit solution and driven at 300 beats/min. The heart was made ischaemic by reducing the flow to 0 ml/min for 25 min, and then reperfused at the constant flow for 15 min. MgSO4 was added to the perfusate for 5 min before the onset of ischaemia, or after the end of ischaemia (after the onset of reperfusion). Ischaemia-reperfusion produced both mechanical dysfunction (as evidenced by an increase in the left ventricular end diastolic pressure and a decrease in the left ventricular developed pressure) and metabolic damage [as evidenced by a decrease in the myocardial adenosine triphosphate (ATP)]. When 15 mmol/l MgSO4 was given before ischaemia, there was no appreciable recovery of mechanical function, whereas when given after ischaemia (during reperfusion), there was a marked recovery of mechanical function. Lower concentrations (10 or 5 mmol/l) of MgSO4 given after ischaemia recovered the mechanical function concentration-dependently. The beneficial effect of 15 mmol/l MgSO4 was minimized by the coexistence of 4.5 mmol/l CaCl2 in the reperfusion solution. The decrease in the myocardial level of ATP induced by ischaemia-reperfusion was attenuated by 15 mmol/l MgSO4 given in the reperfusion solution. These results suggest that high Mg2+ is effective in attenuating both functional and metabolic damage of the post-ischaemic heart, provided it is given after ischaemia.

Effect of NCO-700, an Inhibitor of Protease, on Myocardial pH Decreased by Coronary Occlusion in Dogs

During myocardial ischemia in dogs effects of NCO-700, a protease inhibitor on myocardial pH, were investigated. Ischemia was produced for 90 min by partial occlusion of the left anterior descending coronary artery (LAD). Myocardial pH was measured by a micro glass pH electrode inserted in the subendocardium of the LAD area. Before partial occlusion, myocardial pH was 7.50-7.67. It decreased by 0.65 to 0.86 pH units after partial occlusion. NCO-700 was injected intravenously after 30 min partial occlusion. At a dose of 5 or 20 mg/kg NCO-700 increased myocardial pH, which had been decreased by LAD partial occlusion, by 0.26 or 0.31 pH units, respectively. In the nonischemic myocardium pH increased only 0.03 units. Drug-induced restoration of myocardial [H+] was then calculated. At a dose of 5 or 20 mg/kg NCO-700 restored myocardial [H+], which had been increased by partial occlusion. However, NCO-700 did not attenuate the ischemia-induced elevation of ST segment of the surface electrocardiogram. These observations demonstrate that NCO-700 attenuates myocardial pH depressed by partial occlusion of LAD.