Plasma exudation in conscious dogs with experimental heart failure

The purpose of this study was to determine the effects of bradykinin (BK), substance P (SP) and histamine on plasma exudation in the skin of conscious dogs with and without pacing-induced heart failure. We also determined the role tissue angiotensin I-converting enzyme (ACE) and neutral endopeptidase (NEP) play in modulating these responses. We found that intradermal injection of BK, SP and histamine induced a significant, concentration-dependent Evans blue exudation in normal dogs (p < 0.05). Bradykinin-induced responses were significantly potentiated by captopril (p < 0.05). In contrast, phosphoramidon potentiated BK-induced responses only at low concentrations of BK. Both captopril and phosphoramidon had no significant effects on SP- and histamine-induced Evans blue exudation. BK- and SP-induced responses were significantly attenuated, whereas histamine-induced Evans blue exudation was significantly potentiated in dogs with heart failure. We conclude that heart failure is associated with attenuation of BK- and SP-, but not histamine-induced plasma exudation in the peripheral microcirculation and that these responses are not modulated by tissue ACE and NEP.