The authors showed also that phosphoramidon significantly potentiates neuropeptide-induced airway microvascular leakage at proximal intrapulmonary airways, but not at any other airway level (ibid, p. 945).
There are no available data about the combined action of posphoramidon and histamine and capscaicin. Nevertheless, some authors discuss the mechanisms of interaction between peptidergic and histaminergic stimuli in the pathogenesis of bronchial asthma (Crimi et al., 1995; O'Connor et al., 2004; Kirsch et al., 1992; Crimi et al., 1988). For example, the results of Intalian scientists (Crimi et al., 1995) provided evidence of phosphoramidon role in the mediation of Bradykinin-related responses but not in the mediation of histaminergic effects. Contrarily, capsaicin and phosphoramidon have synergistic effects on the bronchial tone (Sagara et al., 1993).
To determine whether the epithelium influenced the effect of endogenously released and exogenously released substance P on smooth muscle function there is expediently to conduct two different experiments. The first one will test the action of exogenously released substance P and can be conducted in vivo with the administration of substance P via inhalation. The effects of endogenously released substance P could be tested in the in vitro study with isolated tracheal ring where some of them will be processed by the airway epithelium removal.
The major effect of epithelium removal on the contractile response to substance P could be related to the loss of neutral endopeptidase and neuropeptide degradation. This hypothesis also is proved by the numerous experimental studies (Toews et al., 1997; Frossard et al., 1989 etc)
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