DO FUNCTIONAL ALTERATIONS PRECEDE STRUCTURAL CHANGES?
Savage et al4 in our laboratory examined the myogenic tone of femoral vessels harvested from Wistar Kyoto rats rendered uremic by a two-stage, 5/6 nephrectomy procedure. These animals were only mildly uremic and still normotensive. Femoral vessels harvested from these animals were mounted on a pressure myograph and the myogenic tone studied. The uremic vessels had higher myogenic tone compared to sham-operated controls Figure 1. Furthermore, the myogenic tone correlated directly with the degree of uremia. Interestingly, because of the mild degree of uremia, these vessels did not demonstrate any histologic differences compared to controls, indicating that functional changes precede structural ones. Further studies were then carried out using the same model but with rats receiving a nonhypotensive dose of ramipril. When the myogenic tone of the femoral vessels was studied, there were no differences between controls and uremics5.
