Figure 6.

Potential role of the AGTR1 in collateral growth. (A) Representative images showing AGTR1 immunoreactivity (brown) in WKY and SHR control and collateral arteries 3 days after arterial ligation. Relative to same animal controls, a remarkable increase is observed in all wall layers of the WKY but not SHR collateral. (B) Analysis of the percentage of cells with immunoreactivity in each wall layer indicates a statistical increase in all wall layers of the WKY collateral and a decrease in the adventitia of the SHR collateral compared to same animal control artery (n = 3, *P ≤ 0.05). C. Effect of AGTR1 blockade by losartan on collateral diameter enlargement in WKY. Paired comparisons of control and collateral arteries before and 7 days after arterial ligation demonstrated significant collateral enlargement in WKY-untreated animals (*P ≤ 0.001) but not in WKY pretreated with losartan (P = 0.215), which prevents collateral growth in WKY. No effect of losartan was observed on the diameters of control arteries, consequently the open bars are not apparent on the graph (n = 5). The combined data suggest that the upregulation and activation of the AGTR1 is not only correlated with, but is also required for collateral growth in the young normotensive WKY.