Recent developments concerning the mast cell and the mode of action of disodium cromoglycate

Sodium cromoglycate and carbachol-induced bronchoprovocation in asthmatic children

Ten children with mild bronchial asthma underwent bronchial challenge with carbachol on three consecutive days; using a double-blind technique, they were given inhaled saline placebo on the first day and placebo or sodium cromoglycate (SCG) on the second and third days 15 min prior to the bronchial provocation test with carbachol. We did not find any significant difference between the baseline and placebo values, but we did obtain a statistically significant difference when comparing baseline with post-SCG and placebo with post-SCG values. These results demonstrate a protective effect of SCG on carbachol-induced bronchospasm in asthmatic children.

The characteristics of inhibition of histamine release from human lung fragments by sodium cromoglycate, salbutamol and chlorpromazine

1 Three drugs have been tested for activity against antigen-induced histamine release from passively sensitized human lung fragments after increasing periods of pre-incubation before challenge.2 After 30 s pre-incubation, sodium cromoglycate inhibited histamine release in the concentration range 0.2-200 muM, producing a maximum inhibition of 33.0%. As the pretreatment period was extended, tolerance developed in a dose-related manner, resulting in a 48.3% and 82.8% loss of activity of the 200 muM dose after 60 min and 19 h pre-incubation, respectively. Tolerance was independent of extracellular calcium and was poorly reversible. Lung tissue desensitized to cromoglycate was cross-tolerant to the related drug, bufrolin, but not to salbutamol or chlorpromazine.3 In acute studies, salbutamol (0.03-3.0 muM) produced dose-related inhibition of histamine release, with a maximum inhibition of 72.2%. The effect was blocked stereoselectively by 1 muM propranolol, suggesting that it occurred through an interaction with lung beta-adrenoceptors. Increasing the pre-incubation time with salbutamol from 30 s to 19 h did not produce tolerance. Inhibition produced by incubation with salbutamol for 19 h was totally prevented when propranolol was added at the beginning of the pre-incubation period, indicating that it resulted from stimulation of beta-receptors and not from a non-specific or toxic effect. However, studies of reversibility of effect through washing or late addition of propranolol did indicate some change in the nature of salbutamol inhibition with time.4 Chlorpromazine was a weak inhibitor of immunological histamine release. A 100 muM concentration was ineffective after 30 s pre-incubation but its activity increased with time. Pre-incubation of lung fragments with this concentration for 1 h or longer, or with a 1 mM dose for a shorter period, provoked histamine release in the absence of antigen. Effects of chlorpromazine were not reversed by washing.5 The different characteristics shown by sodium cromoglycate, salbutamol and chlorpromazine indicate that these drugs inhibit histamine release by interfering with the secretory mechanisms in different ways.

Eosinophil degranulation. Monitoring by interference contrast microscopy

A method is described for the quantitative monitoring of human eosinophil degranulation using interference contrast microscopy. Using staphyloccoci as a stimulus, degranulated cells appeared larger than nondegranulating cells, were ameboid in shape and exhibited large nude areas of cytoplasm with prominent nuclei. Granules were observed to marginate along the plasma membrane and discharge into the exterior of the cell. Eosinophils that were not induced to degranulate were spherical in shape and the cytoplasm contained numerous granules that often obscured the nuclei. Pharmacological agents that increase intracellular cAMP prevented degranulation, whereas those that increase cGMP had no effect on degranulation. Colchicine inhibited degranulation but did not interfere with the phagocytosis of staphyloccoci. Endotoxin-activated serum, ECF-A, phytohemagglutinin, concanavalin A, levamisole, and compound 48/80 caused degranulation of eosinophils per se. The presence of disodium cromoglycate prevented this degranulation. Compound 48/80 and disodium cromoglycate had no effect on the level of intracellular cAMP and cGMP.

The anti-anaphylactic action of tiaramide hydrochloride

Tiaramide hydrochloride (THC) is a new basic, non-steroidal, anti-flammatory drug. Its anti-anaphylactic action has been investigated using rat mast cells. It was found that THC exerts a strong inhibitory action on antigen-induced and compound 48/80-induced histamine release from rat peritoneal mast cells in a fluorometric assay. Compound 48/80-induced vasodilatation in rat skin is inhibited by prior intradermal injection of THC, as measured by blueing of skin due to intravascular Evans blue dye. THC also inhibits radio-labeled serotonin release from compound 48/80-challenged rat mast cells. In these experimental systems a similar action was exerted by disodium cromoglycate, but higher drug concentrations were needed. Further studies are needed to determine the exact mode of action of this drug and its eventual clinical use in the field of allergic diseases.