The pharmacologic activities of leukotrienes C-i and D (LTC-1 and LTD), constituents of slow reacting substance of anaphylaxis (SRS-A), were evaluated in vitro on airway contractile tissues and in vivo on pulmonary mechanical function, mean systemic arterial pressure, and cutaneous microcirculation. In vitro both LTC-Land LTD were potent and selective peripheral airway agonists, being more active than histamine; furthermore, LTD was active on peripheral airways at concentrations 1/100th those of LTC-1. The concentration-effect relationship for LTD and the profile of antagonism by FPL 55712 are consistent with the activity. of this molecule at two separate peripheral airway receptors. Ii vivo, LTC1 and LTD were nearly equally active in their effects on pulmonary mechanics, and the pattern of alterations was consistent with the predominant site of action being in the lung periphery. Furthermore, both agents had a direct systemic arterial hypotensive effect and were vasoactive on the cutaneous microcirculation. Thus, these compounds are likely to be major mediators of the pathologic alterations in immediate type hypersensitivity reactions in which peripheral airway constriction and hypotension are prominent features.Slow reacting substance of anaphylaxis (SRS-A) (1), which is an activity generated during immediate type hypersensitivity reactions (2), has been found to be composed of leukotrienes C-i (LTC-1) and D (LTD) (3). Native SRS-A has a unique profile of contractile activity in vitro in smooth muscle preparations (4). Both partially and highly purified native SRS-A produced by an anaphylactic reaction in the rat peritoneal cavity (SRS-Arat) exhibit a preferential contractile activity for guinea pig pulmonary parenchymal strips compared to musculus trachealis (5), and LTC-1 and LTD exhibit the same differential effect, at concentrations less than 0.1% of those required for histamine to be active (3). Partially purified SRS-Arat augments vascular permeability when injected into guinea pig skin (6). When administered intravenously into the unanesthetized guinea pig, it produces an alteration in pulmonary mechanics consistent with peripheral rather than central airway action (7). We have now demonstrated that intravenous infusion of LTC-1 and LTD alters pulmonary mechanics in unanesthetized and anesthetized guinea pigs in a manner similar to native partially purified SRS-Arat and that, in addition, these newly described products of arachidonate metabolism (8-10) can differ in their actions on the cutaneous microvasculature and on mean systemic arterial pressure.MATERIALS AND METHODS LTC-1 and LTD were prepared as described (3, 10), sealed in ampoules in 10% methanol under argon, and stored frozen until the day of use. Histamine diphosphate was obtained from Sigma. FPL 55712, a specific SRS-A antagonist, was a gift from P. Sheard (Fisons Pharmaceuticals, Ltd., U.K.).Tracheal spirals and parenchymal strips were prepared for recording isometric contractile activity (5) and allowed to relax to baseline tensi...

Mice have been used in studies of the immunology or pathology of several different disorders affecting the lung. However, the value of the mouse for the analysis of pulmonary pathophysiology has been limited by the lack of methods for measuring lung function in the living animal. We report here the first method for measuring pulmonary conductance (GL) and compliance (Cdyn) in tracheostomized mechanically ventilated mice. We used this method to characterize the mouse's pulmonary responses to several putative bronchoconstrictor agonists. GL and Cdyn were decreased by intravenous infusions of methacholine, norepinephrine, or serotonin. Reproducible responses were not detected after infusions of histamine, prostaglandins D2 or F2 alpha, leukotrienes C4 or D4, substance P, or platelet-activating factor. The pattern of airway responsiveness to these agonists in the mouse is similar to that reported for the rat; in contrast to the rat, the mouse has many well-characterized strains or mutants with deficiencies of immunologic or inflammatory cells or mediators. As a result, this model offers unique advantages for identifying the roles of individual inflammatory cell types or mediators in pulmonary processes, including pulmonary anaphylaxis.

The effects of inhaling nitric oxide (NO) on airway mechanics were studied in anesthetized and mechanically ventilated guinea pigs. In animals without induced bronchoconstriction, breathing 300 ppm NO decreased baseline pulmonary resistance (RL) from 0.138±0.004 (mean±SE) to 0.125±0.002 cmH2O/ml s (P < 0.05). When an intravenous infusion of methacholine (3.5-12 ,ug/kg-min) was used to increase RL from 0.143±0.008 to 0.474±0.041 cmH2O/ml. s (P < 0.05), inhalation of 5-300 ppm NO-containing gas mixtures produced a dose-related, rapid, consistent, and reversible reduction of RL and an increase of dynamic lung compliance. The onset of bronchodilation was rapid, beginning within 30 s after commencing inhalation. An inhaled NO concentration of 15.0±2.1 ppm was required to reduce RL by 50% of the induced bronchoconstriction. Inhalation of 100 ppm NO for 1 h did not produce tolerance to its bronchodilator effect nor did it induce substantial methemoglobinemia (< 2%). The bronchodilating effects of NO were additive with the effects of inhaled terbutaline, irrespective of the sequence of NO and terbutaline administration. Inhaling aerosol generated from S-nitroso-N-acetylpenicillamine also induced a rapid and profound decrease of RL from 0.453±0.022 to 0.287±0.022 cmH2O/ml s, which lasted for over 15 min in guinea pigs bronchoconstricted with methacholine. Our results indicate that low levels ofinhaled gaseous NO, or an aerosolized NO-releasing compound are potent bronchodilators in guinea pigs. (J. Clin. Invest. 1992. 90:421428.)

Maximum expiratory flow rate at 30 percent of vital capacity above residual volume served as an index of airway obstruction in comparing the effects of leukotriene C and histamine administered by aerosol to five normal persons. Leukotriene C was 600 to 9500 times more potent than histamine on a molar basis in producing an equivalent decrement in the residual volume. The leukotriene C response was slow in onset and prolonged, reminiscent of the effects of aerosol allergen challenge in asthmatic allergic subjects.

Two isoforms of prostaglandin G/H synthase (PGHS; prostaglandin endoperoxide synthase, cyclooxygenase) have been identified; PGHS-1 is expressed constitutively in most tissues, whereas PGHS-2 is thought to be induced by various proinflammatory cytokines and growth factors. In this study, we determined which isoform of PGHS mRNA, protein, and activity was present constitutively in A549 (a human lung adenocarcinoma cell line) and in untransformed (normal human bronchial epithelial or NHBE) and transformed (16HBE4o-) human bronchial epithelial cells. Two PGHS-2-specific inhibitors, NS-398 and L-745, 337, blocked the release of prostaglandin E2 from A549 cells with mean inhibitory concentrations of 5 and 18 nM, respectively, but did not inhibit its release from human bronchial smooth muscle cells (BSMC) at a concentration of 10 microM. Northern and immunoblot analysis demonstrated that BSMC expressed PGHS-1 mRNA and protein constitutively, whereas epithelial cells expressed PGHS-2 mRNA and protein constitutively with either undetectable (A549, 16HBE4o-) or very low levels (NHBE) of PGHS-1. We conclude that PGHS-2 is the dominant PGHS isoform in unstimulated and stimulated lung epithelial cells in culture.