LV collagen content (top) and interstitial collagen fraction (ICF; bottom) in 2K-1C hypertensive rats treated with Ac-SDKP for 8 weeks. Collagen content (assessed by hydroxyproline assay) was significantly increased at 8 or 16 weeks after clipping. Ac-SDKP reversed this increase in a dose-dependent manner compared with 2K-1C/vehicle-8W, reaching significance only at a high dose (P<0.001). ICF showed a similar pattern, confirming the collagen data. *P<0.05 vs sham-8W, †P<0.001 vs sham-16W, ‡P<0.05, §P<0.001 vs 2K-1C/vehicle-16W.