TACHYKININ-INDUCED NASAL FLUID SECRETION AND PLASMA EXUDATION IN THE RAT - EFFECTS OF PEPTIDASE INHIBITION

Substance P (SP) evokes fluid secretion and plasma extravasation when applied to the nasal mucosa of rats. SP and another tachykinin, neurok inin A (NKA), are degraded in vitro by neutral endopeptidase (NEP) and angiotensin-1-converting enzyme (ACE). In this study, NKA or SP were applied locally to the nasal mucosa of rats. Subsequent fluid secretio n was measured by a filter paper technique. Plasma exudation was deriv ed as the recovery of intravenous (i.v.) administered I-125-albumin fr om the fluid-containing filter papers. In order to inhibit enzymatic d egradation of the tachykinins by NEP and ACE, the rats were treated wi th i.v. administered phosphoramidon or captopril respectively or their combination. SP evoked fluid secretion that was augmented by phosphor amidon and further enhanced by adding captopril. NKA evoked nasal flui d secretion less effectively than SP and the effect was unaffected by peptidase inhibition. SP, but not NKA, evoked increased plasma exudati on but only after pre-treatment with phosphoramidon.