Angiotensin converting enzyme inhibitors potentiate the bronchoconstriction induced by substance P in the guinea-pig.
1. The effects of intravenous captopril and enalaprilic acid on the increase in pulmonary inflation pressure induced by different bronchoconstrictor agents were evaluated in the anaesthetized guinea-pig. 2. Captopril and enalaprilic acid (1.6-200 micrograms kg-1) enhanced dose-dependently the bronchoconstriction (BC) induced by substance P. The threshold effective dose was 1.6 micrograms kg-1 and maximal potentiation over the control response was more than 400% for both agents. Enalaprilic acid was also assayed for serum and lung angiotensin converting enzyme (ACE) inhibition in anaesthetized guinea-pigs. This drug produced a dose-dependent inhibition of ACE in both tissues, with ED50 s of 7.6 and 9.4 micrograms kg-1, respectively: this inhibitory activity was positively correlated to substance P potentiation. 3. Captopril (8-1000 micrograms kg-1) enhanced dose-dependently the BC induced by capsaicin. The threshold effective dose was 40 micrograms kg-1 and maximal potentiation about 90%. 4. Captopril (200-1000 micrograms kg-1) did not affect BC induced by bradykinin. However, this response was markedly enhanced (about 200%) by captopril 200 micrograms kg-1 in propranolol-pretreated animals. 5. Captopril and enalaprilic acid (200-1000 micrograms kg-1) slightly (20-40%) but significantly enhanced the BC induced by 5-hydroxytryptamine. However, this response was potentiated to the same extent by a dose of prazosin, which produced a degree of hypotension similar to that observed after administration of the ACE inhibitors. 6. In conclusion, ACE inhibitors potentiate the BC induced by substance P and, to a minor extent, that induced by capsaicin in the anaesthetized guinea-pig. Potentiation of substance P is well correlated with ACE inhibition in guinea-pig serum and lungs. These experimental results may offer a mechanistic interpretation of cough and bronchial hyperreactivity observed in patients receiving treatment with ACE inhibitors.
Department of Pharmacology, Laboratori Guidotti S.p.A., Pisa, Italy.
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Guelfi
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Criscuoli
D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001920:Bradykinin / Q000494:pharmacology; D001980:Bronchi / Q000187:drug effects*; D002211:Capsaicin / Q000494:pharmacology; D002216:Captopril / Q000494:pharmacology; D004357:Drug Synergism; D015773:Enalaprilat / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009479:Neuropeptides / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology; D013373:Substance P / Q000494:pharmacology*
D000806:Angiotensin-Converting Enzyme Inhibitors; D009479:Neuropeptides; D012701:Serotonin; D013373:Substance P; D002216:Captopril; D015773:Enalaprilat; D002211:Capsaicin; D001920:Bradykinin; D011224:Prazosin