Antagonism by mefenamic and flufenamic acids of the bronchoconstrictor action of kinins in the guinea-pig

BRONCHOCONSTRICTOR ACTION AND ANTAGONISM OF A SLOW-REACTING SUBSTANCE FROM ANAPHYLAXIS OF GUINEA-PIG ISOLATED LUNG

Slow-reacting substance produced in anaphylaxis (SRS-A) increased resistance of the lungs to inflation in the guinea-pig in vivo and caused isolated preparations of its tracheobronchial muscle to contract. SRS-A also contracted human isolated bronchial muscle and some but not all preparations of rabbit trachea. Nonsteroid anti-inflammatory drugs, which antagonize bronchoconstriction induced by kinins, but not that by histamine, acetylcholine, 5-hydroxytryptamine, substance P, angiotensin or lung prostaglandin, also antagonized the bronchoconstrictor action of SRS-A. This antagonism resembled that of kinins in being surmounted by higher doses of agonist, in the potencies of active drugs and in the types of drugs which were inactive. However, receptors in guinea-pig tracheobronchial muscle for SRS-A seem to be distinct from those for bradykinin, since preparations of this muscle could become unresponsive to either agent in vivo and in vitro, while remaining responsive to the other.

The platelet-independent release of thromboxane A2 by Paf-acether from guinea-pig lungs involves mechanisms distinct from those for leukotriene

Intra-arterial injections of platelet-activating factor (Paf-acether, 10-300 ng) to the perfused guinea-pig lung induced a dose-related bronchoconstriction, followed by contraction of the rat aorta superfused with the lung effluent, indicating the release of thromboxane A2 (TXA2) activity. These effects were matched with injections of bradykinin (Bk) at 100-1000 ng, leukotriene C4(LTC4) at 10-300 ng or arachidonic acid (AA) at 30-300 micrograms. Repeated doses of Paf-acether led to a specific desensitization of the release of TXA2, under conditions where Bk, LTC4 and arachidonic acid retained their ability to release TXA2. Bronchoconstriction and the release of TXA2 induced by Paf-acether were suppressed when the lungs were perfused with acetylsalicylic acid, but not with salicylic acid. The phospholipase A2 inhibitor, p-bromophenacyl bromide suppressed the release of TXA2 by Bk, but did not interfere with its formation from AA, nor with its release with Paf-acether and LTC4. The lipoxygenase inhibitor, nordihydroguaiaretic acid, inhibited to a similar extent the release of TXA2 by Bk, LTC4 and Paf-acether but also reduced directly the formation of TXA2 from arachidonic acid, invalidating its use as a specific antilipoxygenase agent. The leukotriene C4/D4 antagonist, FPL 55712, suppressed the TXA2 releasing effects of LTC4, and was completely inactive against Paf-acether, Bk or arachidonic acid. The aerosol of Paf-acether was tested in the anaesthetized guinea-pig and resulted in bronchoconstriction, unaccompanied by thrombocytopenia. Unlike bronchoconstriction induced by intravenous Paf-acether, which is refractory to cyclo-oxygenase inhibitors, the effects of the aerosol were suppressed by aspirin. Platelet depletion, which blocks the intravenous effects of Paf-acether, failed to interfere with those of the aerosol. Paf-acether induced a marked contraction of the superfused guinea-pig isolated parenchyma lung strip, which was followed by total and irreversible desensitization to itself. The contractile effect was not inhibited by aspirin or indomethacin, atropine, mepyramine, methysergide, phenoxybenzamine or propranolol, indicating that cyclo-oxygenase products, cholinergic stimuli, histamine, 5-hydroxytryptamine and catecholamine mechanisms are not involved. Our results indicate that Paf-acether interacts with pulmonary sites distinct from those for Bk, LTC4 or AA, since no cross-desensitization between Paf-acether and the other agonists was noted, p-bromophenacyl bromide inhibited Bk only and FPL 55712 inhibited only LTC4. The phospholipase A2 involved with the release of the arachidonate needed for the formation of TXA2 by Paf-acether or LTC4-stimulated lungs may differ from the enzyme accounting for its formation by Bk. The cellular sites with which Paf-acether interacts may also be distinct and less readily accessible to p-bromophenacyl bromide.

Nonsteroidal anti-inflammatory drugs: a review. New applications in hypersensitivity reactions of cattle and horses

Nonsteroidal anti-inflammatory drugs inhibit the biosynthesis of kinins and prostaglandins and stabilize leukocyte lysosomal membranes. Nonsteroidal anti-inflammatory drugs also weakly block the biosynthesis of histamine and serotonin, and pharmacologically antagonize kinins, prostaglandins and slow-reacting substance of anaphylaxis. Nonsteroidal anti-inflammatory drugs effectively control both cardiovascular and respiratory manifestations of hypersensitivity in cattle and horses. This, coupled with the contrasting lack of effectiveness of "antiamine" drugs, suggests that bio-amines such as histamine and serotonin (5-hydroxytryptamine) may be less important than kinins, postaglandins and slow-reacting substance in the mediation of the hypersensitivity/inflammatory reaction, at least in cardiopulmonary systems of these species. Nonsteroidal anti-inflammatory drugs justify more prominence in the clinical control of acute respiratory disease in domestic herbivores.

The pharmacology of anaphylaxis in the chicken intestine

1 The Schultz-Dale phenomenon has been demonstrated in several circular smooth muscle strips of oesophagus, crop, duodenum, jejunum and ileum taken from young and adult domestic fowl sensitized actively to crystalline bovine albumin or horse plasma. 2 The ileal strips contract to acetylcholine, histamine, 5-hydroxytryptamine (5-HT), prostaglandins E1, E2, F2alpha, bradykinin and bovine slow reacting substance of anaphylaxis (SRS-A). Marked seasonal and individual variations in the responsiveness of gut tissues to these exogenous agonists were noted. 3 Antagonism of contractions to histamine by mepyramine suggests the existence of H1-histamine receptors in chicken ileum. Blockade of 5-HT-induced contractions by methysergide shows the preponderance of 'D'-musculotropic tryptamine receptors. 4 Failure of selective receptor antagonists of acetylcholine, histamine and 5-HT to modify the Schultz-Dale reaction suggests the nonparticipation of aminergic mechanisms in this reaction. 5 Partial to complete blockade of the Schultz-Dale reaction by a prostaglandin receptor antagonist (polyphloretin phosphate, PPP); prostaglandin synthetase inhibitors (sodium meclofenamate and phenylbutazone); inhibitors of synthesis and release of histamine and SRS-A (PR-D-92-EA, M & B 22948, diethylcarbamazine citrate, and PPP) and an inhibitor of proteinases (aprotinin) strongly suggests the involvement of vasoactive lipids and polypeptides in the anaphylactic response of chicken ileum to specific antigen.

The effects of angiotensin I and angiotensin II on the isolated tracheal muscle of the cat

The effects of Asp1-beta-amide-Val5-angiotensin II (A II) and Asp1-Ile5-angiotensin I (A I) have been studied on the isolated continuously superfused cat tracheal muscle contracted by 5-hydroxytryptamine (5-HT). Both peptides have been shown to induce dose-dependent relaxation on this muscle. Similar effects have been obtained with synthetic bradykinin, prostaglandin E2 (PGE2), noradrenaline and histamine. The effects of bradykinin, A I and A II have been shown to be inhibited by aspirin but not by propranolol, metiamide, SC 19220 or a specific, competitive antagonist of A II. The relaxing effect of A I is not due to the conversion of decapeptide to octapeptide A II. The possible mechanism of the relaxing effects of A I and A II on the cat isolated tracheal muscle is discussed.

Evaluation of cryogenine on rat paw thermal oedema and rat isolated uterus

1. Significant inhibition of oedema formation caused by thermal injury was observed for calcium carbaspirin, phenylbutazone, hydrocortisone, cryogenine and indomethacin when given daily beginning 2 days prior to thermal exposure and afterwards. Several anti-inflammatory drugs, including cryogenine, failed to reduce thermal oedema significantly when given as single doses 1 h prior to the thermal injury.2. Kinetic experiments on the rat isolated uterus demonstrated that cryogenine, chlorpromazine, and flufenamic acid were, in part, competitive inhibitors of synthetic bradykinin, while indomethacin and tetrabenazine showed only non-competitive antagonism.

Response of aspirin-allergic patients to challenge by some analgesics in common use

Challenge tests with some analgesics in common use were performed in five aspirin-sensitive asthmatics. Marked falls in FEV(1) were observed after ingestion of paracetamol, indomethacin, mefenamic acid, and dextropropoxyphene in some subjects. The mechanisms of analgesic-induced asthma are discussed: it is believed to be a non-immunological process of great practical importance when prescribing analgesics to asthmatics.

The use of the in vivo trachea preparation of the guinea-pig to asses drug action on lung

A method for recording the effects of drugs on an isolated in vivo segment of trachea and on lung pressure of a deeply anaesthetized animal is described. Acetylcholine, angiotensin, histamine, 5-hydroxytryptamine, prostaglandin (PG) F2α and slow-reacting substance of anaphylaxis, but not bradykinin, caused an increase in tracheal segment pressure and an increase in lung pressure. Bradykinin caused an increase in lung pressure but a fall in tracheal segment pressure. It was concluded that bradykinin acts mainly on the smaller airways and PGF2α mainly on the larger airways. The tracheal segment responded to adrenaline, aminophylline, ephedrine, isoprenaline, papaverine, PGE1 and PGE2. Propranolol reduced or abolished responses to all these bronchodilators except PGE1 and PGE2.

Antagonism by fenamates and like-acting drugs of bronchoconstriction induced by bradykinin or antigen in the guinea-pig

1. Nine non-steroidal anti-inflammatory drugs were tested for antagonism of bradykinin-induced bronchoconstriction in guinea-pig lungs in vivo. Only one, benzydamine, was inactive.2. The descending order of potency of the active anti-inflammatory drugs was meclofenamate = Scha 306>Scha 87/2>indoxole>Mi85>indomethacin>glafenine>ibufenac.3. Of eight other drugs tested, chlorpromazine, phenoxybenzamine and four others were inactive, whereas phenelzine and mebanazine possessed activity.4. In tests at two dose-levels of meclofenamate, the dose-ratio of bradykinin increased proportionately with the dose of meclofenamate.5. The anti-bradykinin effect of meclofenamate was still observed after destruction of the brain and spinal cord, after bilateral adrenalectomy or after blockade of beta-receptors for adrenaline.6. Meclofenamate did not release catecholamines from the adrenal medulla or prevent such a release by bradykinin given intra-arterially.7. The fenamates and like-acting drugs reduced the intensity of anaphylactic bronchoconstriction in guinea-pigs treated with mepyramine or propranolol. The descending order of potency was meclofenamate>flufenamate>mefenamate.8. Dose / response curves for the antagonism of anaphylactic bronchoconstriction by the fenamates, in the presence of propranolol, turned downwards at high doses.9. These findings suggest that the fenamates may find a useful place in the treatment of bronchial asthma or other conditions involving allergic ventilatory impairment.

The quantiative measurement of motor inco-ordination in naive mice using an acelerating rotarod

A simple modification of the standard rotarod apparatus is described which eliminates the necessity of time-consuming training and consequently gives a truer measure of motor co-ordination since any effects on memory are avoided. The sensitivity and reproducibility of the procedure are much greater than those obtained with constant speed rotarods and less animals are required to obtain statistically significant results.

The influence of analgesic antipyretic drugs on the responses of guinea-pig lungs to bradykinin

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