Influence of experimental chronic hypertension on the cerebral and renal arteries of wild cats.

The influence of chronic hypertension (HT) on the cerebral and renal arteries was examined pathologically and morphometrically in wild cats without a specific genetic background. Chronic HT for 8-15 months was induced by uninephrectomy and salt-loading, and the blood pressure was monitored for a maximum of 5 months. The grade of systolic blood pressure elevation in each cat during the monitoring period was 21-51 mmHg. Histologically, the cerebral arachnoid and medullary arteries of all hypertensive cats showed a well-preserved medial layer, and neither loss of medial smooth muscle cells, adventitial fibrosis or fibrinoid exudation was detected. This experimental model of chronic HT in wild cats for 8-15 months induced segmental intimal elastofibrosis of the arachnoid and renal arteries, but spared the cerebral medullary artery. The parenchymal changes in the brain were negligible. Morphometrically, the arachnoid artery in control cats had a significantly thinner media than the renal artery, and the medial hypertrophy of the arachnoid artery resulting from HT occurred significantly less frequently than that of the renal artery. These findings suggest that the arachnoid and medullary arteries are relatively well protected from HT, and that this may be characteristic of cerebral arteries in general and ascribed to autoregulation.