Possible role of the vascular renin-angiotensin system in hypertension and vascular hypertrophy.

To investigate the vascular renin-angiotensin system in two-kidney, one clip (2K1C) hypertension, we measured angiotensinogen messenger RNA (mRNA) in the aorta and aortic and plasma angiotensin II (Ang II) concentration in 2K1C rats during early (4 weeks) and chronic (16 weeks) phases. Four weeks after clipping, there was no significant change in aortic angiotensinogen mRNA in both groups. However, the levels of plasma and aortic Ang II in 2K1C rats were significantly elevated compared with levels in control rats (p less than 0.05). Sixteen weeks after clipping, aortic angiotensinogen mRNA in 2K1C rats did not differ compared with the level in control rats. The aortic Ang II level in 2K1C rats was significantly increased compared with that in control rats (p less than 0.05), whereas there was no significant difference in the plasma Ang II level between the groups during this chronic phase. During both phases, morphological studies in 2K1C rats showed arteriosclerotic changes, with a significant increase in the wall-to-lumen ratio (p less than 0.01). The present study is the first to demonstrate an increase in vascular Ang II levels and concomitant morphological arteriosclerotic changes during both the early and chronic phases in 2K1C rats. Together with the results of our previous study that demonstrated an elevation of vascular renin activity during the early phase and increased vascular angiotensin converting enzyme activity during the chronic phase, we conclude that the elevated vascular renin activity and vascular angiotensin converting enzyme activity during each phase may play a dominant role in the increase in vascular Ang II observed during both phases.