2.7 Blood pressure measurements in conscious rats
The day before blood pressure measurements, 8-12 weeks old male Wistar
rats were anesthetized by ketamine/xylazine (60 mg
kg-1 / 9 mg kg-1, respectively,i.p ). A polyethylene cannula was inserted into the abdominal
aorta through the femoral artery for blood pressure measurements and
another cannula was inserted into the inferior cava vein through the
femoral vein or in the aorta through the left common carotid artery for
intravenous (i.v. ) or intraarterial (i.a ) administration,
respectively, of BK-(1-9) and its fragments. The cannulas, filled with
saline and closed by metallic pins, were exteriorized in the
interscapular region of the animals’ backs. Rats were individually
housed and left to recover for 24 hours. On the following day, rats were
coupled to a pressure transducer and then allowed to stabilize until
cardiovascular parameters were stable. The cardiovascular parameters
were recorded using the MP 150 Biopac System (Goleta, CA, USA). First, a
dose-response relationship was obtained to assess whether BK-(1-9) and
its fragments were able to elicit biological responses in vivo. In order
to do so, BK-(1-9), BK-(1-7) or BK-(1-5) was administered i.v. as
a bolus (0.1 mL), corresponding to a dose of 2.5 nmol, 5 nmol or 10 nmol
per animal, in sterile saline. Sterile saline was injected at the same
volume, as vehicle control. To further explore the in vivo effect
mediated by BK-(1-9) and its related fragments, a bolus (0.1 mL) of each
peptide was administered, corresponding to a dose of 10 nmol per animal,
in the arterial or venous circulation of adult male rats to assess
whether passage through the pulmonary vascular beds would alter the
response to these peptides. We also decided to test whether in vivo
inhibition of ACE would affect the responses to BK-(1-9), BK-(1-7) and
BK-(1-5). After i.v. administration of captopril (5mg
kg-1, in sterile saline) and stabilization of
cardiovascular parameters, animals were given BK-(1-9) or its related
peptides (0.1 mL, 10 nmol per animal, in sterile saline).