Recovery from hypoxia-induced internalization of cardiac Na+ /H + exchanger 1 requires an adequate intracellular store of antioxidants.

The heart is highly active metabolically but relatively underperfused and, therefore, vulnerable to ischemia. In addition to acidosis, a key component of ischemia is hypoxia that can modulate gene expression and protein function as part of an adaptive or even maladaptive response. Here, using cardiac-derived HL-1 cells, we investigate the effect of various hypoxic stimuli on the expression and activity of Na+ /H + exchanger 1 (NHE1), a principal regulator of intracellular pH. Acute (10 min) anoxia produced a reversible decrease in the sarcolemmal NHE1 activity attributable to NHE1 internalization. Treatment with either 1% O 2 or dimethyloxaloylglycine (DMOG; 1 mM) for 48-hr stabilized hypoxia-inducible factor 1 and reduced the sarcolemmal NHE1 activity by internalization, but without a change in total NHE1 immunoreactivity or message levels of the coding gene ( SLC9A1) determined in whole-cell lysates. Unlike the effect of DMOG, which was rapidly reversed on washout, reoxygenation after a prolonged period of hypoxia did not reverse the effects on NHE1, unless media were also supplemented with a membrane-permeant derivative of glutathione (GSH). Without a prior hypoxic episode, GSH supplementation had no effect on the NHE1 activity. Thus, posthypoxic NHE1 reinsertion can only take place if cells have a sufficient reservoir of a reducing agent. We propose that oxidative stress under prolonged hypoxia depletes intracellular GSH to an extent that curtails NHE1 reinsertion once the hypoxic stimulus is withdrawn. This effect may be cardioprotective, as rapid postischaemic restoration of the NHE1 activity is known to trigger reperfusion injury by producing an intracellular Na + -overload, which is proarrhythmogenic.

Cardioprotective effects of 44Bu, a newly synthesized compound, in rat heart subjected to ischemia/reperfusion injury.

Excessive intracellular Na+ accumulation followed by Ca2+ overload in cardiac tissue is one of the important mechanisms leading to ischemia/reperfusion injury. In the present study, the cardioprotective effects of 44Bu, 2-hydroxy-3-(butylamino) propyl-4-{(butoxycarbonyl)amino}benzoate hydrochloride, a novel Na+ channel blocker, on ischemia/reperfusion injury were investigated and compared to lidocaine. Isolated rat hearts perfused at the constant flow were exposed to global ischemia for 60 min followed by 30 min of reperfusion. In control hearts, ischemia/reperfusion markedly decreased left ventricular developed pressure and increased left ventricular end-diastolic pressure, and caused lactate dehydrogenase release and infarction. 44Bu (0.1, 0.3 and 1 microM) or lidocaine (1 and 200 microM) was administrated during the last 10 min before ischemia and the first 5 min of the reperfusion period. A significant post-ischemic functional recovery in the same degree was elicited by 0.3 and 1 microM 44Bu or 200 microM lidocaine. These effects of 44Bu and lidocaine closely correlated with the reduction in the infarct size and lactate dehydrogenase release. In contrast, 44Bu (0.1 microM) or lidocaine (1 microM) treatment did not result in a significant recovery in any of the examined parameters. In accordance with functional results, our electrophysiological data demonstrated that 44Bu was a more potent agent than lidocaine in terms of transient Na+ current inhibition. On the other hand, 44Bu did not cause any change in Ca2+ currents and on Na+/H+ exchange activity. These results show that 44Bu, as a novel Na+ channel blocker, has cardioprotective effects against ischemia/reperfusion injury.

Synthesis and studies on antidepressant and anticonvulsant activities of some 3-(2-thienyl)pyrazoline derivatives.

In this study, the synthesis of twelve 3-(2-thienyl)pyrazoline derivatives are described. The structures of all compounds were confirmed by UV, IR, (1)H-NMR, mass spectral data, and microanalyses. In the pharmacological studies, antidepressant and anticonvulsant activities of these compounds have been screened. The antidepressant activities of the compounds were investigated by Porsolt's behavioral despair test (forced swimming) on albino mice and compared with tranylcypromine. Among the compounds examined, the compounds 9 and 12 showed significant antidepressant activity. Anticonvulsant activities of the compounds were determined by maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole (metrazol) (scMet.) tests, neurotoxicities were determined by rotarod toxicity test on albino mice. Compound 8 was found to be protective against MES in the range of 30-300 mg/kg dose levels at four hours. None of the synthesized compounds showed neurotoxicity at 30-300 mg/kg dose levels.

Synthesis and studies on antidepressant and anticonvulsant activities of some 3-(2-furyl)-pyrazoline derivatives.

Twelve 1-phenyl-, 1-thiocarbamoyl- and 1-N-substituted thiocarbamoyl-3-(2-furyl)-5-phenyl/(2-furyl)-2-pyrazoline derivatives were synthesized. The chemical structures of the compounds were proved by IR, (1)H NMR, Mass spectrometric data and microanalyses. The antidepressant activities of the compounds were investigated by Porsolt's behavioural despair (forced swimming) test on albino mice. 1-N-Ethylthiocarbamoyl-3-(2-furyl)-5-phenyl-2-pyrazoline (6) and 1-N-allylthiocarbamoyl-3,5-di(2-furyl)-2-pyrazoline (11) reduced 33.80-31.42% duration of immobility times at 10 mg kg(-1) dose level. Anticonvulsant activities of the compounds were determined by maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole (metrazol) (scMet.) tests, neurotoxicities were determined by rotarod toxicity test on albino mice. 1,5-Diphenyl-3-(2-furyl)-2-pyrazoline (2), 1-N-allylthiocarbamoyl-3-(2-furyl)-5-phenyl-2-pyrazoline (7), 1-N-allylthiocarbamoyl-3,5-di(2-furyl)-2-pyrazoline (11) and 1-N-phenylthiocarbamoyl-3,5-di(2-furyl)-2-pyrazoline (12) were active at 100-300 mg kg(-1) dose levels. 1-Thiocarbamoyl-3,5-di(2-furyl)-2-pyrazoline (4), 1-N-methylthiocarbamoyl-3,5-di(2-furyl)-2-pyrazoline (9) and 1-N-ethylthiocarbamoyl-3,5-di(2-furyl)-2-pyrazoline (10) were found protective against MES and scMet. at 30-300 mg kg(-1) dose levels.

Effects of ischemic preconditioning on rat lung: role of nitric oxide.

Recent studies suggest that ischemic preconditioning (IP) of the lung may have a protective effect in ischemia-reperfusion (I/R) injury. The purpose of the present study was to investigate the preconditioning hypothesis in rat pulmonary vascular bed and to examine the role of nitric oxide (NO) in IP. Isolated rat lung was perfused with Krebs-Henseleit solution containing indomethacin at a constant flow rate and perfusion pressure changes was recorded by a pressure transducer. In rat pulmonary vascular bed, 2 hours of hypothermic ischemia significantly attenuated histamine-induced vasodilator responses without affecting sodium nitroprusside (SNP) vasodilation when compared to sham values. However, 2 cycles of 5 minutes of ischemia and reperfusion that were applied prior to 2 hours of ischemia (IP protocol) prevented the attenuation of histamine-induced vasodilation. On the other hand, IP failed to prevent pulmonary edema after ischemia. Histopathological examination of rat lungs demonstrated that IP was able to protect endothelial cells and type II pneumocytes in lung. Moreover, in IP group, malondialdehyde (MDA) contents of the lung tissue were significantly lower and tissue glutathione (GSH) contents were significantly higher than those in I/R group. Administration of NO synthase inhibitor, N(G)-nitro-L-arginine-methyl ester (L-NAME) prior to the IP protocol abolished the protective effects of IP, but not affected the tissue malondialdehyde and glutathione levels. These results suggest that I/R impaired endothelium-dependent vasodilatory response, whereas endothelium-independent SNP-induced responses were preserved in rat pulmonary vascular bed. IP prevented the impairment of pulmonary vascular endothelium-dependent responses, and these effects may be partially mediated by NO.

Preconditioning modulates pulmonary endothelial dysfunction following ischemia-reperfusion injury in the rat lung: role of potassium channels.

Ischemic preconditioning (IP) may protect the lung from ischemia-reperfusion (I/R) injury following cardiopulmonary by-pass and lung or heart transplantation. The present study was undertaken to investigate the role of ATP-dependent potassium channels (K(ATP)) in IP in the isolated buffer-perfused rat lung (IBPR) under conditions of elevated pulmonary vasoconstrictor tone (PVT). Since pulmonary arterial perfusion flow and left atrial pressure were constant, changes in pulmonary arterial pressure (PAP) directly reflect changes in pulmonary vascular resistance (PVR). When compared to control value, the pulmonary vasodilator responses to histamine and acetylcholine (ACh) following 2 h of hypothermic ischemia were significantly attenuated, whereas the pulmonary vasodilator response to sodium nitroprusside (SNP) was not altered. IP in the form of two cycles of 5 min of ischemia and reperfusion applied prior to the two-hour interval of ischemia, prevented the decrease in the pulmonary vasodilator responses to histamine and ACh. Pretreatment with glybenclamide (GLB) or HMR-1098, but not 5-hydroxydecanoic acid (5-HD), prior to IP abolished the protective effect of IP. In contrast, GLB or 5-HD did not significantly alter the pulmonary vasodilator response to histamine without IP pretreatment. The present data demonstrate that IP prevents impairment of endothelium-dependent vasodilator responses in the rat pulmonary vascular bed. The present data further suggest that IP may alter the mediation of the pulmonary vasodilator response to histamine and thereby trigger a mechanism dependent on activation of sarcolemmal, and not mitochondrial, K(ATP) channels to preserve endothelial-dependent vasodilator responses and protect against I/R injury in the lung.

Effect of ischemic preconditioning on reactive oxygen species-mediated ischemia--reperfusion injury in the isolated perfused rat lung.

OBJECTIVE: To investigate the protective effect of ischemic preconditioning (IP) in the early phase of reperfusion injury. DESIGN AND METHODS: Control rat lungs were subjected to 3 h of perfusion, whereas the lungs of the ischemia-then-reperfusion (I/R) group were subjected to 2 h of cold ischemia following 30 min of perfusion. IP was performed by two cycles of 5-min ischemia followed by 5 min of reperfusion prior to 2-h cold ischemia. Lipid peroxidation and antioxidant status were determined in tissue samples. RESULTS: Lipid peroxidation and reduced/oxidized glutathione (GSH/GSSG) ratio were increased; antioxidant enzyme activities were decreased in the I/R group whereas lipid peroxidation and GSH/GSSG ratio were decreased; antioxidant enzyme activities were increased in the IP group. CONCLUSION: IP appeared to have a protective effect against reactive oxygen species-mediated I/R injury in isolated rat lung.