Time Course and Extent of Structural Vascular Adaptation to Regional Hypotension in Adult Spontaneously Hypertensive Rats (SHR)

In female spontaneously hypertensive rats, 8–12 months old and consequently with considerable structural changes in their resistance vessels, the aorta was ligated below the renal arteries, markedly lowering the hindquarter blood pressure. 3, 7, 14, 21 and 135 days later the hindquarters of these rats and of control rats were subject to paired perfusions, from maximal dilatation up to maximal pressor responses, thus exploring hemodynamically the rate and extent of regressive changes in vascular design. ‐ Already after 3 days clear signs of regression of the hypertensive vascular changes were found and in about 3 weeks the resistance vessels had almost completed their considerable adjustment to the low pressure situation, with widened lumina and a reduced bulk of contractile media. However, still after another 17 weeks they displayed signs of a wall /lumen ratio elevation compared with the situation in similarly treated young SHR (Folkow et al . 1971 a). ‐ It is concluded that even though a considerable hypotensive readjustment of vascular design takes place also in adult SHR with established hypertension, it is generally more difficult to induce full regression the higher the age and the longer the duration of the disease, presumably due to the gradual addition of less reversible vascular changes such as collagen invasion of the media.