The effect of prednisolone and ketotifen on the antigen-induced bronchoconstriction and mediator release in rat isolated lungs.

Using a new method for inducing IgE-mediated, systemic anaphylaxis in the rat both prednisolone and ketotifen had been shown previously to be effective in suppressing the bronchial anaphylaxis in vivo. In order to study the mode of action underlying their bronchoprotective effect, both agents were also tested on the antigen-induced bronchoconstriction in rat isolated lungs in relation to the mediator release in the lung-effluent. The presence of histamine, 5-hydroxytryptamine (5-HT) and SRS-A could be detected biologically in the lung-effluent during bronchoconstriction. Histamine and 5-HT were determined quantitatively by means of h.p.l.c. with fluorimetric detection, whereas SRS-A was determined using the guinea-pig ileum in a cascade set-up. Although both prednisolone and ketotifen inhibited the antigen-induced bronchoconstriction effectively, it appeared that only prednisolone suppressed the release of histamine, 5-HT and SRS-A in the lung-effluent significantly, whereas ketotifen had no effect. On account of these data it is suggested that the bronchoprotective effect of prednisolone is mainly based on inhibition of the release of the mediators involved, whereas the effect of ketotifen may be based on receptor antagonism.

The effect of catecholamine depletion on the bradykinin-induced relaxation of isolated smooth muscle.

The effect of depletion of catecholamines by tyramine or reserpine on the bradykinin-induced relaxation of the rat duodenum aan rabbit ileum was the object of this study. The relaxation was not affected by catecholamine depletion due to repeated addition of tyramine to the isolated organs from either normal or reserpine-treated animals. From these findings and on the basis of other data in the literature it can be concluded that the bradykinin relaxation is not due to a release of catecholamines, but rather to a direct effect on the smooth muscle cells.

The mechanism of action of two bradykinin-potentiating peptides on isolated smooth muscle.

Bradykinin-induced contractions in the guinea-pig ileum were potentiated by the peptides A-VI-5 (Val-Glu-Ser-Ser-Lys) and BPP5a (Pyr-Lys-Trp-Ala-Pro), while the contractions induced by other agonists were not affected. Neither peptide added alone caused any response. Previous addition of the peptides shortened the latent period following the addition of bradykinin to a value corresponding to the contraction height with an equivalent dose of bradykinin added alone. Bradykinin in contact with a piece of ileum was inactivated at a relatively slow rate. This inactivation was not inhibited by either A-VI-5 or BPP5a in doses causing potentiation. Suppression of the cholinergic activity by cooling, atropine, morphine or tetrodotoxin did not influence the potentiating activity. Addition of the peptides at the moment a submaximal contraction due to bradykinin had been fully established, increased the contraction height within seconds. The two peptides caused a parallel shift to the left of the dose-effect curve of bradykinin, whereas the maximum bradykinin effect remained unchanged. It is concluded that sensitization of bradykinin receptors due to an increased affinity of the receptor for bradykinin is the hypothesis which best fits the experimental findings.

The bradykinin potentiating activity of two pentapeptides on various isolated smooth muscle preparations.

Two bradykinin potentiating peptides A-VI5 (Val-Glu-Ser-Ser-Lys) and BPP5a (Pyr-Lys-Trp-Ala-Pro), were compared with respect to their potentiation of a number of different bradykinin effects on six isolated smooth muscle preparations. Apart from the considerable difference in effective concentrations, no essential qualitative difference was observed between these two peptides. Therefore the assumption of a different mechanism of action for the two peptides, which have a completely different structure, could not be substantiated.

Further studies on the structure-activity relationships of bradykinin-potentiating peptides.

Several pentapeptides were synthesized and tested for bradykinin-potentiating activity. From these and previous data it appeared that an (L)-aromatic amino acid residue (preferably Trp) in position 3 is essential for high activity. Position 3 represents a stereospecific pillar function, whereas the other positions and the lipophilicity/hydrophilicity balance are important for additional activity. So far, BPP5a seems to have the optimal structure for a bradykinin-potentiating pentapeptide.

Structure-activity relationships of bradykinin potentiating peptides.

A number of A-VI-5 (Val-Glu-Ser-Ser-Lys) analogues and fragments were synthetized and tested on bradykinin potentiating activity so as to establish the nature of the active group(s) or structural characteristics of some bradykinin potentiating pentapeptides. It could be concluded that (1) the polar groups of the side-chains, such as the two hydroxyl groups of the serine residues, the omega-carboxyl group of the glutamic acid residue and the omega-amino group of the C-terminal lysine, are not essential for the bradykinin potentiating activity; (2) the chain length (at least 5 amino acids) and the lipophilicity of the N-terminal amino acid as well as the whole peptide are of much more importance; (3) the free N-terminal NH2-group is not essential; (4) aromatic amino acids in position 3 of the peptide chain result in highly active bradykinin potentiating peptides.

Effect of naloxone on blood pressure and survival in different shock models in rats.

The effect of naloxone on a number of experimental shock models, using the anaesthetized rat, was studied with special emphasis on mean arterial blood pressure (MABP) and chance of survival. Only a slight increase in MABP was noted in haemorrhagic shock models whereas survival was not affected. Naloxone was without effect in endotoxin shock (i.p. administration of endotoxin). In endotoxin shock (i.v. administration) naloxone increased MABP especially at a high dose of endotoxin. Although survival time was prolonged, the chance of permanent survival was not improved. Naloxone had practically no effect in anaphylactic shock and intestinal ischaemia shock. It is concluded that if naloxone has any effect it is relatively slight. However, this does not exclude the possibility that naloxone might still be considered as an adjunct to other forms of shock treatment at least in certain types of shock.

Craving despite extremely high methadone dosage.

A clinical case study is presented of an opiate addict, currently under methadone maintenance treatment (MMT), who claims the need of a higher daily methadone dose. He is admitted to a closed metabolic ward, where he receives 250 mg methadone per day. During 24 h both pharmacokinetic parameters and craving levels are measured simultaneously. Results show extremely high methadone concentrations and its primary metabolite EDDP in plasma and urine. The craving level shows a distinguished peak around the methadone administration on both measured days. Withdrawal symptoms as well as self-reported craving did not correspond at all to the extremely high methadone concentration level in plasma. So we suggest that in individual cases if high methadone doses and plasma methadone levels are not able to diminish craving symptoms, dose adjustment should be accompanied by education regarding daily anticipatory increase of opiate craving.

Craving patterns in methadone maintenance treatment with dextromoramide as adjuvant.

A study was performed to establish the effect on opiate craving among six long-term opiate-dependent subjects in methadone maintenance treatment. Subjects currently stabilised on methadone, received 5 or 10 mg dextromoramide besides methadone. During the study the usual methadone dose was diminished according to the individual subject's expectation of the effect of dextromoramide addition. A clear drug-effect relationship between the increment of dextromoramide plasma concentration and decrement of opiate craving could be seen. A craving increase before drug administration was seen in three cases. The results could imply beneficial effects of a short-acting opiate on diminishing craving in opiate addicts who are difficult to stabilise with methadone maintenance treatment.

Characterization of various antiallergic agents using a new method for inducing systemic anaphylaxis in the rat.

Five different types of antiallergic agents were studied using a newly developed method for inducing IgE-mediated bronchial and cardiovascular anaphylaxis in the rat. With the exception of the histamine H1 antagonist mepyramine (no activity at all), each antiallergic tested showed a different and characteristic profile of antiallergic activity. Prednisolone and the SRS-A antagonist FPL 55712 protected the rats completely against mortality, whereas cromoglycate and ketotifen offered only partial protection. The cardiovascular events were favorably influenced by FPL 55712 and cromoglycate, but ketotifen was completely ineffective in this respect. However, ketotifen showed the highest activity in suppressing the antigen-induced bronchoconstriction, followed by cromoglycate and prednisolone, whereas FPL 55712 was practically inactive. It can be concluded that the antiallergic activity of various types of antiallergics can be characterized and differentiated by means of this highly reproducible method.

A new method for inducing fatal, IgE-mediated, bronchial and cardiovascular anaphylaxis in the rat.

Brown-Norway rats, sensitized with trinitrophenyl (TNP) haptenized ovalbumin and AIPO4 as adjuvant 12 days before, were challenged with trinitrophenyl haptenized bovine serum albumin intravenously, while lung function (Vt, V, Ppl, Fres, Cdyn, and Rl) and cardiovascular function (BP and Fheart) were measured continuously. This resulted in a highly reproducible, plasma IgE-antiTNP related, immediate anaphylactic response characterized by a short-lasting (8-10 min) bronchoconstriction, together with a long-lasting fall in blood pressure. All rats died in shock within 21-150 min. This method is simple and appeared to be highly reproducible and therefore suitable to screen or study antiallergic drugs in vivo.

Rat alpha 2 macroglobulin is a selective inhibitor of antigen-induced leucotrienes in rat isolated lungs.

Exogenously administered, purified rat alpha 2 macroglobulin (alpha 2M, recognized as an acute phase reactant with anti-inflammatory properties) greatly inhibits the increase of the pulmonary resistance during the antigen-induced bronchoconstriction in rats in vivo, whereas a BaSO4 pretreatment (a method to induce a broad spectrum of serum acute phase reactants, including alpha 2M) covers a broader bronchoprotection: suppression of the decrease of the dynamic lung compliance as well. To explain these differences we studied the influence of both alpha 2M and BaSO4 on the antigen-induced bronchoconstriction in rat isolated lungs in relation to the mediator release in lung-effluents. We report here that in this model alpha 2M only inhibits the antigen-induced SRS-A release, whereas the concomitant release of histamine and 5-HT was unaffected. As distinct from alpha 2M the BaSO4 pretreatment suppressed both the antigen-induced bronchoconstriction and the histamine, 5-HT and SRS-A release to a high extent. These data suggest that alpha 2M can be considered as a selective inhibitor of leucotrienes, which offers an explanation for several anti-inflammatory properties of alpha 2M, including protection against the antigen-induced increase of the pulmonary resistance in vivo.

Smooth muscle contracting compounds in the venom of Megascolia flavifrons (Hym: Scoliidae) with notes on the stinging behaviour.

1. The wasp Megascolia flavifrons stings larvae of the stag beetle Oryctes nasicornis on the ventral side of all segments, except the last three, which do not contain nerve ganglia. 2. Experiments indicate a central rather than a peripheral action of the venom. 3. From pharmacological analysis it is concluded that the venom does not contain cholinergic or serotonergic activity, but contains histamine- and bradykinin-like substances. 4. The presence of histamine was confirmed by a radioenzymatic method.

Inhibitory effects of BaSO4 on experimentally induced inflammation in the rat mediated by alpha M-foetoprotein.

The influence was studied of BaSO4 (i.p.) pretreatment on the mediator induced inflammatory responses: oedema formation, measured plethysmographically, increased vascular permeability to protein, measured by the extravascular accumulation of 125I-labeled albumin (125I-HSA) and vasodilatation, measured by the accumulation of 51Cr-labeled erythrocytes. Subplantar application of histamine, 5-hydroxytryptamine, bradykinin or prostaglandin E2 caused oedema formation, an enormous 125I-HSA accumulation and a relatively small 51Cr-labeled erythrocytes accumulation. BaSO4 pretreatment inhibited all these inflammatory responses to a high extent, while the alpha M-foetoprotein (alpha MFP) serum levels were increased from a normal value of 188 +/- 123 micrograms/ml up to 5200 +/- 2264 micrograms/ml (n = 29). From this study and previous data using purified alpha MFP it could be assumed that the anti-inflammatory effects induced by BaSO4 pretreatment are mediated by this enormous increase of the alpha MFP serum levels of alpha MFP are nonspecific and possibly caused by a coating and/or membrane stabilizing effect on cell membranes and/or endothelial junctions.

Efficacy of theophylline and its N-7-substituted derivatives in experimentally induced bronchial asthma in the guinea-pig.

A study has been made of the bronchospasmolytic actions of theophylline and some ot its N-7-substituted derivatives administered by i.v infusion in anaesthetized guinea pigs, in which experimental bronchial asthma was induced by i.v. administration of histamine, 5-hydroxytryptamine and bradykinin. Bronchoconstriction was measured as changes in tidal volume, airflow rate, intrapleural pressure fluctuations and respiratory frequency. Dynamic lung compliance and pulmonary resistance was computed and recorded simultaneously. In addition blood pressure and heart rate were recorded. Theophylline, proxyphylline, diprophylline and etophylline when given alone had hardly an effect on lung function; relatively high doses of the drugs caused a fall in blood pressure and an increase in heart rate. Acephylline infusion in relatively high doses produced a decrease of dynamic lung compliance and an increase of pulmonary resistance. Some animals died. Theophylline, proxyphylline, diprophylline and etophylline were effective in reducing the mediator-induced bronchoconstriction. Protective effects correlated considerably (R = 0.75-0.82) with the plasma concentrations. The magnitude of these protective effects increased with the plasma concentration. Effective doses of proxyphylline, diprophylline and etophylline were much higher than those of theophylline. Acephylline was completely inactive in reversing the mediator-induced bronchoconstriction. At relatively high doses it increased the bronchoconstrictive effects of the mediators. It is concluded that diprophylline, proxyphylline and etophylline, like theophylline, are highly effective bronchospasmolytics, but does of the individual drugs must be adjusted according to the derivative used. Theophylline is by far the most effective of the four compounds. On the basis of this study and recent pharmacokinetic data in man the therapeutic value of acephylline in asthmatics seems doubtful.

Determination and pharmacokinetics of dextromoramide in methadone maintenance therapy.

To study the pharmacokinetics of dextromoramide in long-term opiate addicts on methadone maintenance therapy (MMT) a reverse-phase HPLC technique was developed to monitor dextromoramide and methadone concentrations in plasma simultaneously. After liquid-liquid extraction from plasma, dextromoramide and methadone were determined using a Supelcosil LC-ABZ column and a mobile phase of KH2 phosphate buffer (25 mM, pH 2.5) mixed with acetonitrile (80:20, v/v) and UV detection at 206 nm. The method was found to be sufficiently sensitive, specific and reproducible to apply in six subjects on MMT for many years, receiving orally administered dextromoramide as adjuvant. Pharmacokinetic data sets for dextromoramide in each subject were conducted and analysed further, indicating short elimination half-life values (71 min, range 31-152 min). Contrary to previous studies, in all subjects tested the pharmacokinetics of dextromoramide are best described using an one-compartment model.