Studies on platelet function in bronchial asthma

Part 1. Morphological change and serotonin-releasability of platelets in bronchial asthmatics

Abstract

To clarify the role of platelets at the site of allergic reaction, ultrastructural observation, measurement of plasma serotonin levels and serotonin-releasability of platelets after various stimuli were studied in 29 asthmatics and 6 normal controls. The results were as follows:
1) Plasma serotonin levels were higher during the attack stage than non-attack stage in asthmatics.
2) Morphological changes and the aggregation of platelets were observed by scanning electron microscopy after stimulation with platelet activating factor (PAF), CaI, anti-IgE and anti-IgG.
3) The serotonin-releasability of platelets stimulated by CaI was significantly decreased in severe asthmatics, compared with mild asthmatics and normal subjects (p<0.05). However, there were no significant differences between steroid dependent and non-steroid dependent intractable asthmatics in severe asthma.
4) The releasability of serotonin was decreased in most cases during asthmatic attack and was suppressed by aminophyllin.
5) The serotonin-releasability of platelets stimulated by anti-IgG or Candida antigen was remarkably enhanced after incubation with serum, although releasability was not increased with heat-treated serum.
These results suggest that platelets play an important role in bronchoconstriction induced by various immunological reactions involved with complement activation in the pathogenesis of bronchial asthma.