Herbert G. Johnson

Secretogogue responses of leukotriene C4, D4: Comparison of potency in canine trachea invivo

By the use of close arterial injection of leukotrienes into the circulation supplying the upper cervical canine trachea, it has been possible to assess the secretogogue effects of leukotriene C4, and D4 on mucus secretion. Both LTC4 and LTD4 increased mucus secretion over baseline levels by a statistically significant level (p = less than 0.05). LTD4 was more potent than C4 with relative potencies of 2500, 320, 630, and 500 based on hillock formation (a measure of secretion) at 1, 2, 3, and 4 minutes after injection. The overall difference in potency in this animal model of mucus production was LTD4 greater than C4 by 1000-fold.

Inhibition of histamine release and ionophore-induced calcium flux in rat mast cells by lidocaine and chlorpromazine.

We studied the effects of lidocaine (L) and chlorpromazine (C), two compounds known to affect the binding of calcium to cell membranes, on histamine release and45calcium uptake by purified mast cells upon challenge with the ionophore A23,187 or with compound 48/80. At low concentrations L and C inhibited the Ca++ flux as well as histamine release while higher concentrations caused enhancement in this function. Evidence was obtained that L 10−4M may displace Ca++ from the cell membranes.

Adenosine‐induced secretion in the canine trachea: modification by methylxanthines and adenosine derivatives

1 Adenosine alone at 0.1 and 1.0 mg per tracheal segment stimulated mucus secretion by 52% and 88%, respectively, compared to baseline (P < 0.0001). 2 The site of the potent secretagogue effect of adenosine in canine trachea was consistent with A2 activation. 3 A2 site activation and enhanced secretion were also induced by N‐ethylcarboxamide adenosine and dipyridamole. 4 N6‐R‐phenylisopropyl adenosine (PIA) and 2′,5′‐dideoxyadenosine (ddAdo) inhibited the adenosine‐induced secretion (35% and 42%, respectively). However, when PIA or ddAdo were administered in conjunction with the potent phosphodiesterase inhibitor, methylisobutylxanthine (MIX), the effects of PIA were potentiated and the effects of ddAdo were reversed, yielding stimulation (A2) and antagonism (A1) of secretion, respectively. 5 8‐Phenyltheophylline by aerosol was a very potent antagonist of the secretagogue effect of adenosine (70% inhibition; P < 0.00001).

The Activity of a New, Novel Inhibitor of Leukotriene Synthesis in Rhesus Monkey Ascaris Reactors

The IgE-mediated hypersensitivity to Ascaris antigen in reactor rhesus primates was used to assess the pharmacologic profile of U-60,257, a pyrrole analog of prostacyclin. Whether the compound was given by aerosol or intravenously, it effectively inhibited the bronchopulmonary effects of antigen challenge. Dose responses by the aerosol route showed a dose-dependent inhibition of resistance (RL) and compliance (Cdyn) changes (100% +/- 0 to 10.2% +/- 14.5 for RL and 79.9% +/- 20 to 0% for Cdyn after 15 breaths of 1.0-0.01% solutions delivered into the lungs; n = 16). When administered at 1.0% by aerosol the duration of the inhibitory effect was 6 h (n = 3). Dose-dependent inhibition in both RL (93.3% +/- 5.6 to 69.4% +/- 34.8) and Cdyn (51.4 +/- 40.4 to 47.0% +/- 28.5) was also seen when the compound was given intravenously (5.0-0.01 mg/kg; n = 16). U-60,257 is a selective inhibitor of leukotriene synthesis in in vitro systems. Therefore, the finding of synergism in the inhibition of response of primates to Ascaris between this compound and the H1 histamine blocker diphenhydramine suggests that the leukotrienes may play an etiologic role in this response.

Inhibition of Allergic Reactions by Cromoglycate and by a New Antiallergy Drug U-42,585E

Immediate type hypersensitivity to Ascaris antigen in Rhesus reactor monkeys was used to assess the pharmacologic profile of cromolyn Na (DSCG) and a new inhibitor of IgE-mediated lung function changes (U-42,585E). Two parameters used to measure lung function, respiratory rate increase and tidal volume decrease, were significantly altered in a dose-related fashion by U-42,585E when the latter was administered either by the intravenous, intrabronchial, or the oral route. Oral activity of U-42,585E was demonstrated with doses as low as 5 mg/kg in Ascaris reactor primates.

Leukotriene C4 and Dimethylphenylpiperazinium-Induced Responses in Canine Airway Tracheal Muscle Contraction and Fluid Secretion

Leukotrienes have been implicated as putative mediators in several air way diseases. In previous canine studies it was shown that leukotriene C4 (LTC4) enhanced fluid secretion over baseline values and this enhancement could be blocked by hexamethonium. This indicates that leukotrienes have as one of their actions, stimulation of ganglionic motor neurons. In the present study, we determined that LTC4 acts at a similar site as the specific nicotinic receptor agonist dimethylphenylpiperazinium (DMPP). Both LTC4 and DMPP when given alone enhanced mucus secretion and induced tracheal muscle contraction over control baseline (p less than 0.05). When added to DMPP, LTC4 enhanced the DMPP effect of muscle contraction at 5 and 8 micrograms by a synergistic amount, while the secretion was only additive. The slopes of the dose-response curves for DMPP + LTC4 did not differ by a statistically significant amount. LTC4 and DMPP act on a similar, if not the same, ganglionic receptor.

Activation of Human Eosinophils by Platelet-Derived Growth Factor

Activated eosinophils are believed to be major contributors to the chronic inflammatory sequelae of asthma, but the details of the mechanism of eosinophil activation in vivo are unknown. In our search for physiologically important modes of eosinophil activation, we studied the effects of recombinant human platelet-derived growth factor (PDGF) on human peripheral blood eosinophils. We compared two activation end-points: secretion of granule contents, exemplified by the release of eosinophil peroxidase (EPO), and eosinophil-derived neurotoxin (EDN), and the generation of active oxygen metabolites (O2- production). PDGFc-sis dose dependently stimulated the secretion of large amounts of EPO and EDN from eosinophils. Higher concentrations of PDGF induced a dose-dependent O2- production, especially if the cells were first primed with low concentrations of phorbol ester. These activities were not seen with the AA homodimer of PDGF, suggesting that the activation was receptor dependent. However, several attempts to directly demonstrate the existence of such receptors were unsuccessful. The magnitude of the secretory response to PDGF, and the realization that eosinophils could be easily exposed to this substance as they travel towards the lung, suggests the possibility that this growth factor may be a physiologically important activator of eosinophils in the pulmonary inflammation which is associated with asthma.

Uptake and subcellular localization of tritiated spermine in Escherichia coli

Abstract The uptake of tritiated spermine by intact cells of Escherichia coli , as well as spheroplasts, was energy- and temperature-dependent and resulted in the binding of a portion of the spermine to subcellular components in a form not readily exchangeable with unlabeled spermine under the conditions of the experiment. Essentially all the radioactivity found on the cell walls was readily exchangeable. Results from experiments in which spheroplasts were lysed with digitonin and in which phenol-isolated nucleic acid preparations from the lysates were treated with various hydrolytic enzymes can best be explained by postulating that a small but significant part of the spermine was bound to the DNA while a major portion was bound to RNA. Appropriate controls have shown that reequilibration during isolation did not account for the apparent binding to DNA although spermine is bound to the nucleic acids as a salt and is displaced especially from RNA even by moderate concentrations of monovalent cations. The implications of the proposed attachment of spermine to DNA in vivo with respect to the mechanism of the antimutagenic action of spermine are discussed.

The synthesis of 6,9-deepoxy-6,9-N-phenylimino-Δ6,8-prostaglandin I1 a novel inhibitor of leukotriene C and D synthesis

The pyrrole analog of prostacyclin, 6,9-deepoxy-6,9-N-phenylimino-delta 6,8-prostaglandin I1 was synthesized from PGF2 alpha methyl ester. This pyrroloprostacyclin (U-60,257) and its methyl ester (U-56,467) have been shown to inhibit leukotriene C/D biosynthesis and antagonize leukotriene C/D contractions in vitro. Antigen induced bronchopulmonary changes in monkeys and guinea pigs are inhibited by U-60,257 in vivo.

Diphenhydramine blocks the leukotriene-C4 enhanced mucus secretion in canine tracheain vivo

Leukotrienes (C4, D4) have been shown to enhance mucus seeretion in both isolated human airway tissue and intact canine tracheain vivo. They also have been implicated as putative mediators in several airways diseases. In previous canine studies the mucus enhancing effect of leukotriene-C4 was blocked by atropine, FLP 55,712, and hexamethonium but not by cutting the superior laryngeal and vagus nerves. We anesthetized mongrel dogs with chloralose (100 mg/kg) and urethane (500 mg/kg) and ventilated them on a pump. To visualize the secretions from submucosal glands, we exposed the mucosa of the upper trachea and coated its surface with powdered tantalum. Seeretions from the glands formed elevation in the tantalum layer (hillocks) with time: the number of tracheal hillocks (an index of mucus secretion) was measured at one or more of the four time points on six dogs after each treatment of the treatment sequence: no LTC4, LTC4, no LTC4+ blocker, and LTC4+ blocker. The potential blocker was diphenhydramine, an H1 antagonist for histamine. LTC4 was injected into the cranial thyroid artery which directly feeds the tracheal segment. We observed hillocks through a dissecting microscope, and the number of hillocks per 1.2 cm2 were counted for a 1–4 min interval. In 6 dogs with 12 responses, LTC4 (10 μg) gave a positive response that was significantly different from control (p<0.01–0.05) at 2–4 min.Diphenhydramine (n=6), 0.5 mg/kg, a dose which blocked a histamine challenge without blocking an acetylcholine challenge of secretion, gave a statistically significant (p<0.01–0.05) reduction in mucus secretion at 1–4 min. These results support the conclusion that leukotriene C4 induces mucus secretion in dogs that is blocked by prior diphenhydramine administration. This would indicate histamine has a role, but as yet an unknown mechanism in the action of leukotriene-C4 in enhancing mucus.