Change of the activities of angiotensins I and II on the vascular smooth muscle by crude kallikrein.
Incubation in vitro of angiotensin I (A I) with crude kallikrein induced a potentiation in the response to decapeptide of the isolated continuously superfused rabbit aorta. Crude kallikrein when incubated with angiotensin II (A II) caused a decrease in response to octapeptide of the same assay tissue. Converting enzyme inhibitor, SQ 20881, produced a competitive inhibition in the response to A I preincubated with crude kallikrein but did not alter the inhibitory effect of the enzyme on A II response. Pure kallikrein did not induce any change in the responses to both peptides when used at the same concentrations. The competitive inhibitor of A II (N,N-dimethyl) Gly1-Ile5-Ile8-angiotensin II (DMGIA II), abolished the effects of both A II- and A I-preincubated with crude kallikrein. From these results it was concluded that crude kallikrein-induced potentiation in the response to A I of the aorta is probably due to the conversion of decapeptide to octapeptide by an enzyme fraction in crude kallikrein preparation. These results also indicate that crude kallikrein (Padutin) is not a pure enzyme preparation and probably contains some other enzyme fractions which are responsible from the changes of the vascular activities of angiotensin-peptides.
D000803:Angiotensin I / Q000494:pharmacology*; D000804:Angiotensin II / Q000494:pharmacology*; D000809:Angiotensins / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology*; D007610:Kallikreins / Q000494:pharmacology*; D007700:Kinetics; D010477:Perfusion; D011817:Rabbits; D013329:Structure-Activity Relationship
D000809:Angiotensins; D000804:Angiotensin II; D000803:Angiotensin I; D007610:Kallikreins