Administration of pharmacological agents and measurement of blood pressure
Mice were randomly assigned to treatment groups. Angiotensin II was dissolved in 0.9 % saline and infused S.C. by osmotic minipump (Alzet model 2002 or 2004) at 0.7 mg/kg/d. Control mice for angiotensin II infusion received 0.9% saline. Aldosterone was dissolved in 87 % propylene glycol, 9 % ethanol and 4 % Milli-Q water and administered S.C. to some mice by osmotic minipump (Alzet model 2002) at 0.72 mg/kg/d. Control mice for aldosterone treatment were infused with 87 % propylene glycol, 9 % ethanol and 4 % Milli-Q water. Mice that were administered vehicle or angiotensin II were maintained on normal drinking water. Mice that were administered aldosterone had their drinking water replaced with 0.9 % saline after minipump implantation.
Mice were anaesthetised with isoflurane (2-4 % inhaled with oxygen, 0.4 L/min) for ~20 min. Adequacy of anaesthesia was monitored by observing respiration and checking for a reflex response to a toe pinch. An osmotic minipump was implanted S.C. in the mid-scapular region for infusion for 14 or 28 d. At the time of surgery, mice were administered bupivacaine (2.5 mg/kg S.C.) at the surgical site and carprofen (5 mg/kg S.C.). Mice then received carprofen (5 mg/kg S.C.) daily for 2 days after surgery. A subset of angiotensin II-infused mice received hydralazine hydrochloride (50 mg/kg) in their drinking water during the 14-d osmotic minipump infusion, or as an intervention at 2 weeks following the commencement of angiotensin II infusion.
Systolic blood pressure was monitored in conscious mice via tail cuff plethysmography (MC4000 Multichannel system, Hatteras Instruments). Prior to surgery, mice were trained for 1 d (i.e. on day -1) to acclimate to the procedure, and blood pressure was then recorded on days 0 (prior to surgery), 3, 7, 14, 21 and 28 of angiotensin II or aldosterone infusion.