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Rats were exposed to hyperbaric oxygen (HBO = 100% oxygen; 2.5 atmospheres absolute pressure) for 6 h. Isovolumic left heart preparations from these animals were subjected to global low flow-ischemia (perfusion rate from 12 ml/min to 2 ml/min for 40 min) and reperfusion. Hearts from rats not exposed to HBO underwent the same ischemic-reperfusion procedure (controls). As compared to control, HBO treatment caused in ex vivo hearts a significant aggravation of cardiac ischemic picture as indicated by a marked increase in left ventricular end diastolic pressure (LVEDP) and reduced post ischemic left ventricular developed pressure (LVDP). At the end of the ischemic and reperfusion periods LVEDP values were 6.8 (p < 0.001) and 8 (p < 0.001) times higher than the corresponding control values. Moreover, LVDP and coronary perfusion pressure (CPP) values were decreased (2.8 times; p < 0.001) and increased (56%; p < 0.001), respectively, as compared to control preparations. These events were also associated with a considerable impairment of the cardiac tissue to generate 6-keto-PGF1 alpha. Treatments of rats with different doses of acetylcysteine (N-acetylcysteine, CAS 616-91-1, NAC; 0.25-0.5-1 g/kg p.o.) before HBO displayed a clear-cut and dose-related protective activity in hearts subjected to ischemia-reperfusion. Also the generating capacity of 6-keto-PGF1 alpha from these hearts were restored according to the dose of NAC employed. When aortic rings from rats exposed to HBO were considered, they showed a reduced capacity to release 6-keto-PGF1 alpha and an increased sensitivity to endothelin-1. At the same time, the relaxant activity of acetylcholine in these tissues was almost lost. Again, NAC treatment of the animals before HBO restored in a dose-dependent way the capacity of the aortic rings to generate 6-keto-PGF1 alpha. This event was paralleled by normalized responses of the preparations to endothelin-1 and acetylcholine. Taken together these results clearly indicate that acute HBO treatment of the rats markedly aggravates the ischemic-reperfusion damage in ex vivo hearts. This event is coupled with a compromised integrity of cardiac and extracardiac endothelial cell functions. The protective activity of NAC observed in this study once more emphasises its therapeutic role in increasing antioxidant defence mechanisms.

The exposure of ovalbumin sensitized guinea-pig to an areosol of the specific antigen causes a respiratory crisis in approximately 100 s (dispnoea time) associated with a substantial increase in blood concentration of both histamine (from 27.5 +/- 1.8 ng/ml to 1570 +/- 26 ng/ml; n = 8) and thromboxane B2 (TXB2, from 0.52 +/- 0.03 ng/ml to 18.1 +/- 0.6 ng/ml; n = 8). The aerosol treatment of the animals (20 min) with furosemide (CAS 54-31-9, frusemide, FRU), nimesulide (CAS 51803-78-2, NIM), acetylsalicylic acid (CAS 50-78-2, ASA) and indometacin (CAS 53-86-1, INDO) at the concentrations of 1-3-10 and 30 mg/ml, before ovalbumin challenge, brought about an attenuation of anaphylactic response. The rank order of potency for the prolongation of dyspnoea time was FRU > NIM > ASA > INDO. In these experiments blood evaluation performed at the peak of the dyspnoea time for histamine concentration in the treated animals indicated that whereas FRU (ED25 = 2.14 mg/ml (1.97-2.38) and NIM (ED25 = 2.74 mg/ml (2.37-3.19)) were equiactive in reducing the release of histamine, ASA and INDO were devoid of this activity. On the contrary, the results obtained with ASA and INDO indicated a greater intrinsic activity in antagonizing TXB2 formation than that shown by the log-dose response curves of NIM and FRU. In another series of experiments the interaction of FRU with the other anti-inflammatory drugs in protecting guinea-pig from immune bronchoconstriction has been evaluated using the combination of two equiactive doses. The mixture considered were FRU+NIM, FRU+INDO and FRU+ASA. The results obtained indicated that FRU interacts positively with the three non-steroidal anti-inflammatory drugs in delaying the onset of the dyspnoeic crisis in guinea-pig. However, when FRU was combined with NIM the gain obtained (209%) appeared superior to that reached when FRU was combined with ASA (180%) or INDO (126%). Taken together these results suggest that non-steroidal anti-inflammatory compounds given by aerosol may represent a valid pharmacological intervention in protecting guinea-pig from anaphylactic bronchoconstriction.

In anaesthetized ventilated guinea-pig, acetaldehyde (CAS 75-07-0) (40-80 mg/kg i.v.) elicits a dose-dependent increase in intratracheal pressure accompanied by an increase in circulating histamine. When acetaldehyde is injected repeatedly at 15 min intervals in capsaicin-desensitized animals, it already loses its activity at the second administration (50% reduction; p < 0.01); this does not happen in control animals. This phenomenon is even more marked when acetaldehyde is given at the dose of 80 mg/kg i.v., since at the third injection both the bronchoconstriction and the increase in blood histamine are almost completely reduced to baseline values. The increase in intratracheal pressure caused by acetaldehyde (20, 40, 80 mg/kg i.v.) is associated with a dose related increase in microvascular permeability and leakage of protein-bound Evans blue in lower tracheal tissue. This event and the bronchoconstrictor response caused by acetaldehyde (40 mg/kg i.v.) are 87% and 35% inhibited, respectively, (p < 0.01) in tachykinin-depleated animals. On the contrary, thiorphan (2 mg/kg i.v.) remarkably potentiates both the rise in intratracheal pressure (110%; p < 0.01) and Evans blue extravasation (215%; p < 0.01) induced by acetaldehyde (20 mg/kg i.v.) in normal guinea-pigs. Furthermore, treatment with CP-96,345, a selective tachykinin NK1-receptor antagonist, only prevents plasma extravasation in lower tracheal tissue (82% inhibition; p < 0.01) without affecting the bronchoconstriction caused by acetaldehyde (40 mg/kg i.v.).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde administered intravenously at various doses (20, 40 and 80 mg/kg) elicits a dose-dependent increase in intratracheal pressure (ITP) and a proportional rise in histamine blood concentration in anaesthetized guinea-pigs. Similar effects were observed in ovalbumin-sensitized guinea-pigs upon aerosol of acetaldehyde (20 mg/ml) which has been administered at the flow rate of 0.1 ml/min for 2 min. Theophylline (CAS 58-55-9) antagonized both the increase of ITP values and the rise of histamine in the blood caused by acetaldehyde given intravenously (ED50 = 5.8 mg/kg i.v.) or by aerosol (ED50 = 4.9 mg/kg i.v.). Furthermore, in animals where combined treatment with pyrilamine (2 mg/kg i.v.) and captopril (2 mg/kg i.v.) resulted in a remarkable potentiation of the bronchoconstrictor response to acetaldehyde (20 mg/kg i.v.), the administration of theophylline (5 mg/kg i.v.) or of the substance P (SP) receptor antagonist, [D-Pro4, D-Trp7.9] SP 4-11 (10 mg/kg i.v.) reduced the augmented action of acetaldehyde on respiratory airways induced by captopril by more than 50%. Moreover, the bronchoconstriction induced by acetaldehyde (40 mg/kg i.v.) was also associated with a significant increase of extravasation of Evans blue in tracheal tissue. Both these effects of acetaldehyde were inhibited by theophylline (10 mg/kg i.v.), whereas a NK1-TK (neurokinin 1-tachykinin) receptor antagonist (412 micrograms/kg i.v.) reduced (81%; p < 0.001) only the vascular permeability changes caused by acetaldehyde.(ABSTRACT TRUNCATED AT 250 WORDS)

Nimesulide (4-nitro-2-phenoxymethane sulfonanilide, Aulin, Mesulid) is a non-steroidal anti-inflammatory compound which shows antihistaminic activity and inhibits the immune release of histamine. The antihistaminic activity of this compound is specific for H1-receptor and has been demonstrated on isolated strips of guinea-pig trachea and on histamine-induced multiphasic inotropic response in left atria of guinea pig electrically driven. The effect of nimesulide is of non competitive type and, at the concentration of 1 x 10(-5) mol/l, is nearly 2 time less potent than pyrilamine (mepyramine) at 1 x 10(-6) mol/l. Nimesulide (1.6 mumol/kg i.v.) inhibits both bronchoconstriction (69%) and TXB2 formation (93%) induced by histamine (0.05 mumol/kg i.v.) in anaesthetized guinea-pigs. In contrast indomethacin (1.6 mumol/kg i.v.) decreases the generation of TXB2 (89%) without affecting the enhancement in tracheal insufflation pressure induced by histamine. In actively sensitized guinea-pigs both nimesulide and indomethacin protect the animals from deadly anaphylactic crisis. The rise in tracheal pressure induced by the antigenic challenge is inhibited of 80% and 63% respectively by nimesulide and indomethacin (6.4 mumol/kg i.v.). At this dose the two compounds reduced of 90% approximately the immunological release of TXB2 in the circulation. The release of histamine, induced by the anaphylactic reaction caused in perfused lungs obtained from actively sensitized guinea-pigs, is lessened by nimesulide (EC50 = 3.06; fid. lim. 2.59-3.63 mumol/l) and potentiated by indomethacin (EC50 = 0.89; fid. lim. 0.67-1.17 mumol/l).(ABSTRACT TRUNCATED AT 250 WORDS)

The general pharmacological profile of levodropropizine (S(-)3-(4-phenyl-piperazin-1-yl)-propane-1,2-diol, DF 526), a new antitussive drug, was compared with that of dropropizine racemate. Levodropropizine had weaker central sedative effects than the racemate and it did not induce physical dependence in rats. When given intravenously or intraperitoneally, levodropropizine did not exert any significant effects on the cardiovascular and respiratory systems. Receptor binding data excluded interaction with beta-adrenergic, muscarinic and opiate receptors. On the contrary, levodropropizine has affinity for H1-histaminic and alpha-adrenergic receptors. The affinity was also confirmed with isolated organ preparations. On the basis of this study, levodropropizine appears to have a better tolerability index than the racemate.

Resistance to lung inflation and blood pressure were monitored together with biological and radioimmunological determination of circulating thromboxane A2 (TxA2) in anaesthetized guinea-pig. Bamifylline, a 2-benzyl-[4,5-d]-imidazopyrimidine derivative, and theophylline were compared for their antagonistic activity against the pulmonary effect of histamine (0.05 mumol/kg i.v.), leukotriene C4 (LTC4, 0.016 mumol/kg i.v.), platelet-activating factor (PAF, 0.0002 mumol/kg i.v.) and acetylcholine (0.1 mumol/kg i.v.). Bamifylline, as well as theophylline, showed a dose-dependent antagonistic activity against both bronchoconstriction and TxA2 generation induced by the above agonists. However, except for histamine where the two compounds were equiactive, bamifylline was 2 times more potent than theophylline. The maximal inhibitory activity was found against bronchoconstriction induced by PAF (ED50 = 6.5 mumol/kg i.v.) followed by histamine (ED50 = 9.5 mumol/kg i.v.), acetylcholine (ED50 = 24.3 mumol/kg i.v.) and LTC4 (ED50 = 31.6 mumol/kg i.v.). Bamifylline (3, 10, 30, 100 mumol/kg i.v.) and theophylline (3, 10, 30, 100 mumol/kg i.v.) protected guinea-pig from antigen-induced bronchoconstriction and TxA2 generation in ovalbumin actively sensitized animals. Also in this series of experiments bamifylline was more potent than theophylline, the ED50 being 9.3 mumol/kg i.v. and 22.9 mumol/kg i.v., respectively. These pharmacological data represent new support for the protecting effect of bamifylline against respiratory damage induced by well known anaphylaxis mediators.

Administration of 6-aminoindazole (6-AIN) and 5-aminoindazole (5-AIN) to rats depressed gastric acid secretion, both basal and carbachol-stimulated. 6-AIN proved to be more active than 5-AIN in decreasing the stimulated secretory process. The antisecretory activity of 6-AIN appears to be partially an antihistamine effect, since this compound antagonized the stimulatory action of betazole on isolated guinea pig auricle. The antisecretory activity of 6-AIN is probably associated with an antimuscarinic effect, since the molecule decreased carbachol-stimulated gastric acid secretion in rats and depressed neostigmine-stimulated motility of duodenum and colon in the anaesthetized cat. It also lessened the hypertonus of isolated guinea-pig trachea caused by pilocarpine. The antisecretory effects of 6-AIN also appear to be associated with myolytic activity, since it decreased the spontaneous motility of duodenum and colon in anaesthetized cats and the spontaneous myoactivity of isolated jejunum of the rabbit. It depressed the contractions of isolated guinea-pig ileum caused by histamine and decreased the spasmogenic effects of barium chloride on isolated guinea-pig gall bladder. These results suggest that 6-AIN probably depresses gastric acid secretion by interfering with both histamine and acetylcholine receptors and with other receptors involved in the secretory process.

In this study 2-guanidinebenzimidazole (GBI) and 1-phenylbiguanide (PBG) appear to be capable of decreasing gastric acid secretion, while the compounds dimethylbiguanide and cyanoguanidine do not. Thus, the antisecretory effect is present when the biguanide groups are associated with lipophilic molecules. GBI and PBG depress gastric acid secretion, even when it has been stimulated by carbamoylcholine (carbachol) or betazole. The antihistamine effects of GBI and PBG on betazole-stimulated gastric acid secretion were confirmed by the inhibitory activity of these compounds on the isolated guinea pig auricle stimulated by histamine. The antimuscarine activity of GBI and PBG on carbachol-stimulated gastric acid secretion in rats is also supported by the way in which these same drugs depress the motility of the duodenum and colon of the anaesthetized cat stimulated by prostigmine. The above mentioned effects of these compounds are also associated with myolytic activity, since they decrease the spontaneous and histamine-stimulated motility of the duodenum and colon. GBI and PBG probably depress gastric acid secretion by interfering with both histamine and acetylcholine receptors and with other sites involved in the secretory process.

S-(+)-2-(4-Fluorophenyl)-alpha-methyl-5-benzoxazolacetic acid (flunoxaprofen, Priaxim is a new antiinflammatory compound, which in various biological systems interferes with the generation and release of arachidonic acid metabolites of the cyclo-oxygenase pathways without affecting the formation of 5- and 12-lipoxygenase products. Flunoxaprofen reduces the concentration of thromboxane (TX)B2 (ED50 = 35.4 mg/kg p.o.) and prostaglandin (PG)E2-like activity (ED50 = 39.9 mg/kg p.o.) in the inflammatory exudate of rats 8 h after implantation of sponges soaked with carrageenan, whereas the concentration of leukotriene (LT)B4 remains in the range of that of the untreated animals (3.1 ng/ml). Flunoxaprofen inhibits cell infiltration in the exudate and this suggests that LTB4 does not initiate cell recruitment but may represent a mechanism for amplifying the inflammatory response. Using human platelets challenged with collagen, flunoxaprofen only at higher concentration (10(-4) mol/l) reduces TXB2 formation without altering generation of 12-hydroxy-5,8,10,14-eicosatetraenoic acid. This suggests a low capacity of flunoxaprofen of affecting platelet aggregation regulated by arachidonic acid metabolites. Flunoxaprofen prevents pulmonary changes due to secondary release of TXA2 in the guinea-pig. In fact this drug prevents changes due to immunological reaction and antagonizes bronchoconstriction due to exogenous administration of histamine and LTC4.(ABSTRACT TRUNCATED AT 250 WORDS)

Tiaramide hydrochloride (THC) is a benzothiazoline derivative with a remarkable antianaphylactic activity: in anaesthetized guinea-pig it shows protecting effects against histamine (H)- and bradykinin (Bk)-induced bronchoconstriction, preventing increase of lung resistance and decrease of dynamic compliance. At the same time THC inhibits formation of circulating thromboxane A2 brought about by H and Bk. THC is also able to antagonize the contractions induced by CaCl2 on isolated guinea-pig tracheal spirals and its mode of action seems to be of the competitive type. Furthermore THC abolishes the "tonic" phase of K+-induced contractions of guinea-pig taenia coli which are dependent on inward movement of calcium, whereas the "phasic" component of the contractions is left unaltered. THC is a very weak inhibitor of 3'-5' cyclic adenosine monophosphate phosphodiesterase which is affected only at very high dosage (10(-2) M). The calcium antagonistic activity of THC may explain both its bronchodilating and antianaphylactic properties.

Unlike testosterone propionate and norandrostenolone decanoate, some new androstane derivatives did not cause any weight increase of the levator ani muscle and of the seminal vesicles in castrated rats. Actually, these new androsterone derivatives, characterized by the presence of a carboxyl group in the position 2 and a hydroxyl group in the 11 alpha or beta position, have entirely lost their affinity for the androgenic receptors of the prostate and of the skeletal muscles.

2-Carbodecyloxy-17 alpha-methylandrosta-1,4-dien-11 beta,17 beta-dihydroxy-3-one (decylroxibolone, BR 917) is a new androstane derivative, esterified with decyl alcohol, carrying a methyl group in the 17 position, a hydroxyl group in the 11 beta position and a carboxyl group in position 2. Unlike norandrostenolone decanoate, decylroxibolone did not cause any weight increase of the levator ani muscle and of the seminal vesicles in castrated rats, nevertheless exerting a marked antiglucocorticoid activity. This new steroid agent can consequently act positively on the nitrogen metabolism, being concurrently devoid of undesired virilizing anabolic effect.