Search

The effects of d -cis- and l -cis-diltiazem on the hydrogen peroxide (H2O2)-induced derangements of mechanical function and energy metabolism, and accumulation of intracellular Na+ were studied in isolated rat hearts. The intracellular concentration of Na+ ([Na+]i) in the myocardium was measured using a nuclear magnetic resonance technique. H2O2 (600 μM) increased the left ventricular end-diastolic pressure, decreased the tissue level of ATP, and increased the release of lactate dehydrogenase from the myocardium. These alterations induced by H2O2 were significantly attenuated by d -cis-diltiazem (15 μM) or l -cis-diltiazem (15 μM). H2O2 (1 mM) produced a marked increase in the myocardial [Na+]i, which was effectively inhibited by tetrodotoxin (3 μM), d -cis-diltiazem (15 μM) or l -cis-diltiazem (15 μM). These results suggest that both d -cis- and l -cis-diltiazem protect the myocardium against the H2O2-induced derangements in the isolated, perfused rat heart. The protective action of d -cis- and l -cis-diltiazem may be due to their ability to inhibit the H2O2-induced increase in [Na+]i, at least in part.

モルモット単一心室筋細胞のNa電流 (INa) に対するbepridilの作用を吸引電極法を用いて検討した.bepridilは-140mVの静止状態から-30mVへの脱分極により活性化されるINaを用量依存性に減少させた (解離定数369μM) .本用量曲線は保持電位を-90mVにすると低濃度側へ平行移動した.2連パルス法によるINaの遮断発現過程実験では, 本剤は4msの条件パルスではINaを14%遮断し, 16ms以上では不活性化状態のINaをより顕著に遮断した.本剤は顕著な使用依存性抑制を示し, INa遮断が定常状態に達するまで迅速であった.定常状態におけるINaの不活性化曲線は, 本剤10μMにより11mV過分極側に偏位したが, 勾配因子は不変であった.不活性化されたINaの回復過程は, -140mVにおいて290msの時定数を示した.以上より, bepridilはNaチャネルの静止状態よりも不活1生化状態に高い親和性を有するが, 活性化チャネルブロックも一部もたらすこと, チャネルからの解離が速いことが明らかとなった.

Bradykinin was injected retrogradely into a branch of the splenic artery of lightly anesthetized dogs, and the reflex hypertensive response was used as an indicator of the nociception. The reflex hypertensive response to low doses of bradykinin (less than 1 nmol), but not to high doses (3-5 nmol), was markedly suppressed by infusion of indomethacin (0.54 mumol/min) into the splenic artery. During indomethacin infusion, the reflex hypertensive response to low doses of bradykinin was potentiated dose dependently by the following arachidonic acid metabolites (ED50): prostaglandin (PG)I2 (2.9 nmol) greater than or equal to PGH2 (4.4) greater than PGE2 (14) = thromboxane (TX)A2(15) greater than PGD2 (greater than 100). Leukotrienes B4, C4 and D4 showed practically no activity. This potentiating effect lasted up to 20 min after injection, particularly with PGE2. These results may not exclude the role of PGI2 as a major candidate for involvement in bradykinin-induced nociception, although a selective TX synthetase inhibitor (OKY-046) showed a weak analgesic effect (only 1/30 that of indomethacin).

Anti-aggregating activity of 7-ethoxycarbonyl-6,8-dimethyl-4-hydroxymethyl-1(2H)-phthalazinone (EG 626) was tested using rabbit platelets in vitro. EG-626 alone, when added before, prevented platelet aggregation induced by ADP, as did PGI2, papaverine and dipyridamole. Spontaneous disaggregation was also accelerated when EG-626 was added after the maximal aggregation induced by ADP. EG-626 alone also inhibited platelet aggregation induced by collagen and arachidonic acid. ID50s of these agents in ADP-induced aggregation were 7-9 nM for PGI2, 223 microM for EG-626, 266 microM for papaverine and 957 microM for dipyridamole. When EG-626 was used in combination with PGI2, a threshold dose (50 microM) of EG-626 potentiated the antiaggregation effect of subthreshold dose (3 nM) of PGI2 upto 100% inhibition in collagen-induced platelet aggregation. The marked potentiating effect of EG-626 was accompanied by an accumulation of cyclic AMP in the platelets. These effects might be due to inhibition of phosphodiesterase. Papaverine and dipyridamole, other phosphodiesterase inhibitors, also potentiated the anti-aggregating activity of PGI2. The activity of papaverine, however, was one eighth of EG-626 and that of dipyridamole was much less. The most effective combination of PGI2 and EG-626 to induce 50% inhibition was obtained with 20% of ID50 of each agent, whereas that of PGI2 and papaverine or dipyridamole was 39 or 41%, respectively.

The activity of prostaglandins (PG) in producing vascular permeability was quantitated by dye extraction method in skin of anaesthetized rabbits. PGE1 and PGE2 (0.01–10 μg) produced increase in vascular permeability. Activity was approximately equal to that of histamine (Hist) and 1 20 of that of bradykinin (BK) on a weight basis. The activity of PGF1α and PGF2α was only 1 20 of that of PGE1 or PGE2. In spite of the relatively low potency of PGE1 and PGE2 in the rabbit, near threshold doses (0.1 or 1 μg) of PGE2 could potentiate permeability responses to bradykinin (0.1 μg) by 10 or 100-fold, respectively. Equivalent doses (0.1 or 1 μg) of histamine could not potentiate the bradykinin responses. Arachidonic acid (AA) at 1 μg, produced a 10-fold potentiation in the permeability response to bradykinin (0.1 μg). Pretreatment of the rabbits with indomethacin (20 mg/kg, i.p.) reduced the responses of BK (0.1 μg) + AA (1 μg) down to a similar magnitude of those seen with bradykinin alone. However, indomethacin did not block responses to either, BK alone, BK + PGE2, or BK + Hist. Various doses (1, 10, 100 and 300 μg) of arachidonic acid alone also produced increase in cutaneous vascular permeability, although its potency was only 1 3 – 1 8 of that of PGE2. This activity of arachidonic acid was attributed in part to its bioconversion to PGE2, since its activity was significantly reduced by the prostaglandin antagonist, diphloretin phosphate (DPP) (60 mg/kg, i.v.) and by indomethacin (20 mg/kg, i.p.), which blocks conversion of arachidonic acid to prostaglandins. Arachidonic acid may owe some of its permeability increaseing effects to histamine release, since its effects were also reduced by the antihistamine, pyrilamine (2.5 mg/kg, i.v.).

A single platelet thrombus was formed in an arteriole of the hamster cheek pouch by electrical stimulation followed by topical application of ADP. The sizes of the thrombi were continuously recorded with a photocell placed on a TV monitor screen and quantified by areas on the record. Repeated application of small doses of ADP (5–15 nmol/10 μl) resulted in very reproducible formation of the thrombi, and the size of the thrombi was reduced dose-dependently by topical application of PGI2. Three drugs were tested in this model. Cycloxygenase inhibitor (indomethacin 10 mg/kg, i.p.) increased the formatiion of thrombi, while a smaller dose (3 mg/kg) did not have any significant effect. This could be explained by inhibition of the generation of endogemous PGI2, since aggregation of hamster platelets by ADP was not inhibited by indomethacin in vitro . EG-626 (phthalazinol, a phosphodiesterase inhibitor) (300 mg/kg, i.p.) decreased the size of thrombus. AI-122 (1.0 mg/kg, i.p.) which has been proven to enhance PGI2 biosynthesis from isolated rat aortae, also decreased the formation. Thus, drugs such as EG-626 or AI-122 are quite promising as anti-thrombic drugs.

Twenty-four drugs, consisting of antipsychotics, tricyclic antidepressants, other centrally acting drugs, and related compounds, were studied for their effects on aggregation of rabbit platelets. Phenothiazine neuroleptics, haloperidol, sultopride, tricyclic antidepressants, sulpiride, atropine, and propranolol showed a selective inhibitory effect on the collagen-induced aggregation, but not on aggregations induced by arachidonic acid (AA) or adenosine diphosphate (ADP). These drugs are thought to inhibit the liberation of AA from phospholipids in platelet membranes, suggesting that they might inhibit phospholipases. Mepyramine, promethazine, phentolamine, and clozapine inhibited the aggregations evoked by collagen and AA, but failed to inhibit the ADP-induced aggregation. These drugs might inhibit the generation of prostaglandin endoperoxides or thromboxanes. Phenobarbital, phenytoin, procaine, lidocaine, flurazepam, trihexyphenydil, and lithium carbonate did not inhibit any kind of aggregation at the concentrations used. The clinical and pharmacological significance of these findings is discussed; it seems that the inhibitory effects of antipsychotics and antidepressants on platelet aggregation are closely related to the specific clinical and psychotropic effects of these drugs, but not to other actions.

During the experiments observing the drug effects on the steady potential of various brain structures, the authors (1) found that the steady potentials of certain subcortical structures such as the hypothalamus and hippocampus were more sensitively altered by psychopharmacological agents than the EEG activity in the same areas. Although many attempts (2-4) have been made to explain the steady potential, its physiological significance has been still unknown. The authors have been interested in this electrical phenomenon from their belief that changes in the steady potential would indicate the CNS activity in some different way from EEG changes. In order to elucidate the correlation between a steady potential and EEG in the various states of activity of the brain, the more primitive brain structure seemed desirable to persue. The authors thus selected the olfactory bulb, because this structure showed a distinct afferent activity in response to olfactory stimulation and its excitatory as well as inhibitory states could be easily demonstrated. Ottoson (5, 6) has observed a slow potential elicited by odoriferous stimulation in the olfactory epithelium as well as in the olfactory bulb. Ottoson's slow potential is regarded as a DC potential change in this structure. The present study was conducted to ascertain the effects of drugs on the DC potential, slow potential and EEG activity of the olfactory bulb, in the hope of elucidating if any mutual correlations of these electrical phenomena exist.

Rat IgE pleurisy was induced by the injection of dinitrophenol-conjugated bovine serum albumin (DNP-BSA) 48 hours after the intrapleural injection of rat anti-DNP-IgE serum. IgG-BSA complex pleurisy was also induced by the intrapleural injection of IgG-BSA complexes produced at the optimum ratio in vitro . Plasma exudation was markedly increased in the first 20 minutes, but not observed thereafter, in IgE pleurisy, whereas marked plasma exudation in the first 20 minutes was followed by weak exudation at three and five hours in IgG-BSA complex pleurisy. Leukotrienes (LTs) E4 (100 ng/rat), D4 (32) and B4 (16) were detected on HPLC in the pleural exudate in the first 20 minutes of IgG-BSA complex pleurisy, but less (9 ng/rat) LTE4 alone was detected in the five-hour exudate. The first 20-minute pleural exudate contained 13 ng/rat of LTE4 in IgE pleurisy. The plasma exudation for the initial 20 minutes in IgE pleurisy was completely inhibited by simultaneous treatment of rats with pyrilamine (2.5 mg/kg, i.p.) and methysergide (3 mg/kg, i.p.), as it was in compound 48/80-induced pleurisy. In IgG-BSA complex pleurisy, 90% of the pleural exudate for the first 20 minutes was inhibited by the same treatment, and the rest was completely suppressed by simultaneous treatment with an intrapleural injection of AA-1777, a selective 5-lipoxygenase inhibitor. AA-1777 alone did not reduce the plasma exudation significantly. The 5-lipoxygenase inhibitor was also very effective in reducing the migrating numbers of polymorphonuclear and mononuclear leukocytes to half, without affecting the eosinophils or mast cells.

The effects of chlorpromazine (CPZ) and imipramine (IMP) on platelet aggregation in vitro were investigated. Both CPZ and IMP inhibited epinephrine-induced secondary aggregation in a dose-dependent fashion and changed adenosine diphosphate (ADP)-induced irreversible aggregation into a reversible response in human platelets. With rabbit platelets, CPZ (0.6-20 microM) and IMP (6-60 microM) showed a selective inhibitory effect on the aggregation by collagen, whereas, even at 200 microM, this effect was found neither in arachidonic acid (AA)-induced aggregation nor in ADP-induced one. CPZ and IMP also inhibited human platelet aggregations induced by collagen, but not by AA. The antiaggregating action of CPZ and IMP was thought to be due to their inhibitory effects on AA liberation from platelet membranes, suggesting that they might inhibit participating enzymes (phospholipase A2, C or lipase) or the process of the activation of the enzymes.

Intrapleural injection of 2% λ-carrageenin caused the accumulation of exudate up to 19 hr. The rate of plasma exudation, measured by the exuded dye amounts for 20 min in the pleural cavity after intravenous injection of pontamine sky blue, showed a peak at 5 hr. Aspirin (100 mg/kg, i. p.) suppressed the dye exudation up to 5 hr, but did not at 7 hr. This inhibition coincided with the decrease of the PG and TXB2 levels, which were measured by gas chromatography-mass spectrometry, in the pleural exudate. In vitro experiments, MK-447, a phenolic compound, stimulates PG endoperoxide biosynthesis at lower doses and inhibits it at higher doses, acting as a tryptophan-like cofactor required by PG endoperoxide synthetase. This drug (0.3, 1.0 and 3.0 mg/kg, i. p.) suppressed the dye exudation dose-dependently up to 5 hr, but did not at 7 hr even at a higher dose, in combination with the dose-dependent decrease of the pleural level of PGE2, which was reported to be a major PG among PGs and TXB2 in the exudate in inducing the plasma exudation (Harada et al ; Prostaglandins, 23 : 881, 1982). Thus, the anti-inflammatory action of MK-447 can be explained by inhibition of PGE2 generation, giving no consideration to the role of oxygen-derived free radicals as a prime mediator in inflammation.

Pleurisy was induced in rats after intrapleural injection of 2% λ-carrageenin. The volume of the pleural exudate increased rapidly between 1 and 3 h, continuing to increase until 7 h. The dye amounts exuded into the pleural cavity for 20 min after 5% pontamine sky blue (60 mg/kg, i.v.) increased markedly at 1 to 3 h, then they kept constant until 6 h, decreasing thereafter. The PGE level in the pleural fluid increased rapidly during the period from 1 to 3 h, when the exudate commenced to accumulate, and then decreased slightly until 7 h. The main PG in the pleural fluid was recognized as PGE2 on thin-layer chromatography. The pretreatment of rats with a PG synthetase inhibitor, indomethacin (5 mg/kg, i.p.), 30 min before carrageenin administration resulted in the significant reduction of dye leakage at 1 h and of the pleural fluid exudation at 1 to 3 h. The intravenous injection into rats of stem bromelain (10 mg/kg, i.v.), a SH-protease from pineapples, caused the depletion of high molecular weight kininogen in plasma without effect on the content of low molecular weight kininogen. The pretreatment of rats with bromelain 30 min before carrageenin caused a marked reduction in the dye exudation during the periods from 1 to 3 h and 5 to 6 h. The accumulation of the exudate was strongly suppressed at the same periods. Although each treatment by itself did not completely abolish the dye and fluid exudation, the treatment of rats simultaneously with indomethacin and bromelain resulted in suppression of dye leakage from 1 to 6 h and practically no fluid accumulation was observed until 4 h. These results strongly indicate that prostaglandin is released in combination with bradykinin at the period when the pleural exudate commences to accumulate.

Pleurisy was induced by intrapleural injection of 0.1ml of 2% λ-carrageenin in male rats(SD strain, SPF, 8-9weeks). Complement titers were measured by Lachmann’s method(50% hemolysis, CH50), using EAC142, which was made by preincubation of erythrocytes with zymosan-treated serum. Complement titers in pleural exudate, expressed in terms of mg protein, were lower than those in serum during the whole course. Considering the in vitro complement activation of rat serum with carrageenin, it could be concluded that complement was activated in pleural cavity. Pleural exudate accumulation began rapidly 1-3 hr after carrageenin injection. Polymorphonuclear leucocytes (PMN) increased their numbers rapidly up to 5 hr and stayed at the same level thereafter, whereas mononuclear leucocyte (Mono) numbers increased gradually up to 24 hr. Using dexamethasone(arachidonic acid(AA) release inhibitor), benoxapro-fen(a lipoxygenase inhibitor with a weak cyclooxygenase inhibition) and K-76COONa(an inhibitor of complement activation), it could be concluded that PMN migration was induced by arachidonic acid metabolites and activated complements. Mono migration particularly in the late phase might be induced by lipoxygenase products.

As an inflammatory model, rat carrageenin-induced pleurisy was used. The pleural exudate was collected 5 hr after the injection of the 2% λ-carrageenin solution to the right pleural cavity. After measurement of the exudate volume, the extraction of leukotriene (LT) and HETE was performed by addition of 4-fold volumes of ethanol. This crude extract caused the very slow contraction of the guinea-pig (GP) ileum, which was similar to that of LTC4 and was inhibited by FPL55712(1 μg/ml). For further puriflication, LTC4 and LTD4 in the sample were separated as 80% ethanol eluate with Sepahdex LH-20 and LTB4, and HETEs were extracted with diethylether. After evaporation, the purified samples dissolved in methanol were applied to high perfomance liquid chromatography. The peaks, coinciding to the retention time of LTC4 and LTD4, respectively, were collected for examination of the contraction on GP ileum. The contraction by the sample was also inhibited by FPL55712. When the ratios of the contractile activity over the peak height on HPLC were compared, the values of the two peaks of the sample were similar to those of LTC4 and LTD4, respectively. LTB4 in the pleural fluid at 5 hr was smaller than 5,12-diHETE. Several mono-HETEs were also found. These results show the presence of LTC4 and LTD4 in the pleural fluid at 5 hr. As LTC4 and LTD4 are potent in plasma exudation, they might play a role in the carrageenin-induced pleurisy at 5 hr.