Arterial structural changes with verapamil in spontaneously hypertensive rats

Reducing pulse pressure might be more powerful than reducing mean arterial pressure to obtain regression of vascular hypertrophy. However, this hypoth esis has never been investigated in the conduit arteries of intact hyperten sive animals. A group of 4-week-old spontaneously hypertensive rats (SHR) w as treated with the calcium-entry blocker verapamil (50 mg/kg) for 16 weeks and compared with untreated SHR and control Wistar Kyoto (WKY) normotensiv e rats of the same age. At the end of the experiment, intraarterial thoraci c aorta blood pressure was measured both in the conscious and anesthetized animals. Carotid artery diameter and stiffness (echo-tracking techniques) a nd aortic histomorphometry were determined in parallel. With verapamil, pul se pressure, but not mean arterial pressure, was significantly decreased bu t did not reach the normotensive values. Carotid internal diameter, medial thickness, and collagen content were significantly reduced by comparison wi th SHR and did not differ from the values of the WKY group. A significant p ositive and independent correlation was observed between pulse pressure and medial thickness in the overall population. The study shows that, in SHR c hronically treated with verapamil, structural changes may be completely pre vented without any change in mean arterial pressure. The parallel change in pulse pressure might suggest that mechanosensitive elements within the vas cular wall may be selectively sensitive to the dynamic aspects of physical forces and are able to convert frequency and amplitude information into cel lular responses that lead to vascular remodeling. (C) 1999 American Journal of Hypertension, Ltd.