PURIFICATION AND BIOLOGICAL-ACTIVITY OF ALLIGATOR BRADYKININ

Incubation of plasma from the alligator (Alligator mississipiensis) with glass beads in the presence of a kininase inhibitor resulted in the activation of the kallikrein-kinin system and generation of bradykinin-like immunoreactivity. The kinin peptides were purified to homogeneity and were shown to comprise [Thr6]bradykinin and des-Arg9[Thr6]bradykinin in the molar ratio of approximately 10:1. Bolus injections of synthetic [Thr6]bradykinin into the jugular vein of the anesthetized alligator resulted in a dose-dependent decrease in mean arterial blood pressure. The minimum dose of kinin producing a significant fall in pressure was 0.07-mu-g/kg body wt and the maximum response (25 +/- 6% fall; mean +/- SD, n = 8) was produced by a dose of 0.56-mu-g/kg body wt. The dose producing a half-maximum response was 0.19 +/-0.08-mu-g/kg. The data indicate that alligator plasma contains all the components of the kallikrein-kinin system found in mammals and suggest that the system may be of physiological importance in the regulation of cardiovascular function in these reptiles.