Evaluation of a direct blood pressure measurement technique for canine toxicity studies.

Repeated direct puncture of the central ear (intermediate auricular) artery to obtain mean arterial blood pressure in control and hypertensive dogs was evaluated. Unilateral nephrectomy and partial constriction of the contralateral renal artery were performed on four dogs to create hypertension. Ear artery blood pressure measurements and electrocardiograms were recorded twice pretest and after surgery at Weeks 1, 2, 4, 6, 8, 9, 10, and 11 on control (n = 6) and hypertensive (n = 4) dogs. Mean ear arterial blood pressures from the hypertensive dogs were significantly increased from Weeks 2 to 11. Indwelling omocervical artery catheters were implanted in both control and hypertensive dogs at Week 8. Mean omocervical artery blood pressures from hypertensive dogs were significantly increased at Weeks 8 through 11. Mean omocervical artery pressures were only significantly increased over mean ear artery pressures at Week 8 for control dogs and at Week 10 for hypertensive dogs. Nonspecific electrocardiographic changes in the ST-T segment and U waves occurred with greater frequency in hypertensive dogs than in control dogs. Hypertensive dogs developed subendothelial proliferation in the renal artery and aorta, and a proliferative vasculopathy in the heart and lungs. This ear artery technique was used successfully in two canine toxicity studies of different ICI pharmaceutical compounds. The ear artery method for measuring mean arterial blood pressure is suitable for canine toxicity studies and is a reasonably accurate measurement of systemic pressure.