Ea. Garrison et al., ANALYSIS OF RESPONSES TO ANGIOTENSIN PEPTIDES IN THE HINDQUARTERS VASCULAR BED OF THE CAT, American journal of physiology. Heart and circulatory physiology, 37(6), 1995, pp. 2418-2425
Responses to angiotensin I, II, III, and IV, des-Asp(1)-angiotensin I,
and (p-amino-Phe(6))-angiotensin II were compared in the hindquarters
vascular bed of the cat. The peptides produced dose-related increases
in perfusion pressure, and dose-response curves to all six peptides w
ere parallel. Des-Asp(1)-angiotensin I, angiotensin I, II, and III pro
duced similar increases in perfusion pressure and were similar to 300-
fold more potent than (p-amino-Phe(6))-angiotensin II, 100-fold more p
otent than angiotensin IV, 30-fold more potent than norepinephrine, an
d 10-fold more potent than U-46619. The time courses of the response t
o des-Asp(1)-angiotensin I, angiotensin I, II, and III were similar, a
nd responses were not altered by a time-delay coil. DuP-532, an AT(1)
receptor antagonist, reduced responses to the six angiotensin peptides
. PD-123,319 did not alter responses to the angiotensin peptides. The
angiotensin-converting enzyme inhibitor captopril reduced responses to
angiotensin I and des-Asp(1)-angiotensin I. These results show that d
es-Asp(1)-angiotensin I as well as angiotensin I, II, III, and IV have
similar efficacy and that responses to the peptides and (p-amino-Phe(
6))-angiotensin II are mediated by AT(1) receptors. These results sugg
est that AT(2) receptors have little role in modulating responses and
that angiotensin IV has a lower affinity for the AT(1) receptor than d
oes angiotensin II or III. The results also indicate that complete rap
id local conversion of the substrates into active peptides occurs near
the site of action within the hindquarters vascular bed.