15-min mean values and are reported as mean 1 h values± s.e. of the mean. Adrenalectomy Rats were anaesthetized with sodium pentobarbital (55 mg kg 1, i.p.). The back of the animal was shaved and a 1.5-cm dorsal midline incision made with its midpoint centered over the thirteenth rib. The underlying muscle wall on either side of the spinal column was dissected, and the adrenal glands were located and removed. Skin incisions were closed with stainless steel wound clips and acute haemodynamic measurements made as described above. Isolated vascular tissue experiments The descending thoracic aorta was removed from rats, cleaned of connective tissue and cut into 3 mm rings. The endothe- lium was left intact, and rings were subsequently mounted (using stainless steel triangle mounts) in 5 mL isolated organ chambers (Radnoti Glass, Monrovia, CA, USA) containing modified Krebs solution (in mM: 120 NaCl, 5.9 KCl, 2.5 CaCl2, 1.2 MgSO4, 1.2 KH2PO4, 25 NaHCO3, 10 glucose) at 371C and aerated with 95%O2:5%CO2. Mounted rings were connected to isometric force transducers (Radnoti Glass). Passive tension was set to an optimal resting tension of 0.5–1 g, and rings were allowed to equilibrate for 30 min. Isometric tension was monitored and recorded using IOX data acquisition software (EMKA Technologies Inc., Falls Church, VA, USA). Rings were tested for viability using 120 mM KCl, washed and allowed to re-equilibrate for an additional 30 min before performing concentration–response curves to test compounds. Perfused hindlimb preparation Rats were anaesthetized with urethane (800 mg kg 1, i.p.) and a-chloralose (40 mg kg 1, i.p.). A midline incision (3 cm long) was made in the lower abdomen to expose the bifurcation of the abdominal aorta. The right iliac artery and vein were isolated and cannulated with modified PE-50 catheters. The arterial catheter was connected to a peristaltic pump (ML 172; ADInstruments, Newton, NH, USA), the speed of which was set to generate a perfusion pressure of 60–70 mm Hg. Perfusion pressure was monitored using a pressure transducer (DTX plus TNF-R; Becton Dickinson) connected to a side arm of the arterial catheter. Initially, the hindlimb was perfused with buffer alone (Krebs-Henseleit solution) to obtain a steady baseline. Subsequently, the hindlimb was sequentially perfused with torcetrapib (3– 30 mM) followed by phenylephrine (5 mM), each for a duration of 5 min with a 2 min interval between treatments. The pressure signal was captured by a Ponemah physiological data acquisition system (P3 Plus; Data Science International, St Paul, MN, USA). Mean perfusion pressure was derived by the software automatically and recorded continuously throughout the study. Measurement of plasma adrenal steroids Adrenal steroid concentrations in plasma samples were determined using commercially available ELISA kits. The Aldosterone and pressor responses to torcetrapib MJ Forrest et al 1467 aldosterone assay was obtained from Alpha Diagnostics (San Antonio, TX, USA) and the corticosterone assay from Cayman Chemical Company (Ann Arbor, MI, USA). Adrenal steroid release assay The procedure for isolating rat adrenal cells was developed by modifying previously published methods (Fredlund et al., 1975). Adrenal glands were removed from male rats, asphyxiated by CO2 and placed in ice-cold Dulbecco’s phosphate-buffered saline. The glands were dissected free of all fat and connective tissue. Each gland was dissected in half, and the outer capsule separated. Each capsule was placed in 1.2 mL of room temperature medium (one part Krebs-Ringer bicarbonate (mM: 120 NaCl, 4.6 KCl, 0.5 MgCl2, 0.7 Na2HPO4, 1.5 NaH2PO4, 10 glucose) with two parts Medium-199 and two parts L-15 plus 5 mM HEPES) contain- ing collagenase (2 mg mL 1) and DNAse (0.4 mg mL 1). The capsules were teased apart in this solution and incubated with gentle rocking for 70 min at room temperature. Every 20 min, cells were gently dispersed by drawing the solution up and down into a silicon tubing of 10 inch length. The suspensions were washed twice in Dulbecco’s phosphate buffered saline following centrifugation at 100 g for 10 min. Finally, the cells were re-suspended in 1.0 mL medium containing BSA (4 mg mL 1) and soybean trypsin inhibitor (2 mg mL 1). The final cell concentration was approximately 200 000 cells per mL. Cell suspensions (500 mL per well) were placed in a 24-well polystyrene plate to which stimuli were added. The plate was incubated in a water bath at 371C for 2 h. Cell suspensions were centrifuged at 1000 g for 10 min, and the media assayed for aldosterone and corticosterone as described above. Test compounds Torcetrapib, anacetrapib and E-3174 were synthesized at Merck Research Laboratories. The endothelin (ETA/ETB) antagonist, compound A (Nishikibe et al., 1999), was synthesized at Banyu Pharmaceuticals, Tsukuba, Japan. Trilostane was purchased from Chempacific (Baltimore, MD, USA). Results Effects of CETP inhibitors on vascular haemodynamics The effects of torcetrapib and anacetrapib on blood pressure were evaluated in normal mice that do not contain CETP and in transgenic mice expressing the cynomologus CETP gene (Figure 1). Administration of torcetrapib (10 mg kg 1) by i.v. infusion of 30 min duration evoked a significant increase in mean arterial blood pressure of approximately 15 mm Hg. The increase in blood pressure was transient, returning to near baseline levels by the conclusion of the infusion. In both normal B6 mice and B6-Tg(CETP) mice, heart rate decreased transiently by approximately 20% (data not shown) following administration of torcetrapib, presumably a reflexogenic response to the increase in blood pressure. In contrast, administration of anacetrapib (10 mg kg 1) or British Journal of Pharmacology (2008) 154 1465–1473