Releases of bradykinin and substance P by heating hind paw of rat

Contribution of kallikrein-kinin system to heat-induced substance P (SP) release into the periphery was studied by using plasma kininogens-deficient strain Brown Norway Katholiek (B/N-Ka) and normal strain Brown Norway Kitasato (B/N-Ki) rats. Bradykinin (BK) and SP levels in the sc perfusates of the hind instep were measured by radioimmunoassay. In B/N-Ki rat, immersion of hind paw into hot water (47 degrees C) for 20 min led to an increase of BK (43 +/- s 34 fmol.min-1) and SP (11.1 +/- 9.7 fmol.min-1) in the perfusate, whereas those in B/N-Ka rat (BK 1.3 +/- 1.0 fmol.min-1 (P < 0.01), SP 5.5 +/- 3.5 fmol.min-1 (P < 0.05)) were remarkably less. Heat-induced extravasation (leakage of Evans blue) in B/N-Ka rat was also less than that in B/N-Ki rat (P < 0.05). Results suggest that kallikrein-kinin system is involved in the release of SP into the periphery, ie, BK released into the extravascular space by noxious heat stimulation intervenes in SP release.