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Effect of early versus late AT1 receptor blockade with losartan on postmyocardial infarction ventricular remodeling in rabbits.
- Source :
-
American Journal of Physiology: Heart & Circulatory Physiology . Jul2009, Vol. 297 Issue 1, p375-386. 12p. 1 Chart, 12 Graphs. - Publication Year :
- 2009
-
Abstract
- To characterize the temporal activation of the renin-angiotensin system after myocardial infarction (MI) in rabbits, we examined cardiac ANG It type 1 receptor (AT1R) expression and ANG II levels from 3 h to 35 days. The effects of losartan (12.5 mgkg-1· day-1) on functional and histomorphometric parameters when treatment was initiated early (3 h) and late (day 15) post-MI and maintained for different periods of time [short term (4 days), midterm (20 days), and long term (35 days)] were also studied. AT1R expression increased in the MI zone at 15 and 35 days (P < 0.05). ANG II levels increased (P < 0.05) in the non-MI zone at 24 h and in the MI zone as well as in plasma at 4 days and then progressively decreased until 35 days. The survival rate was significantly lower in untreated MI and early long-term-treated animals. Diastolic pressure-volume curves in MI at 35 and 56 days shifted to the right (P < 0.05). This shift was even more pronounced in long-term-treated groups (P < 0.05). Contractility decreased (P < 0.05 vs. sham) in the untreated and long-term-treated groups and was attenuated in the midterm-treated group. The early administration of losartan reduced RAM 11-positive macrophages from 4.15 ± 0.05 to 3.05 ± 0.02 cells/high-power field (HPF; P < 0.05) and CD45 RO-positive lymphocytes from 2.23 ± 0.05 to 1.48 ± 0.01 cells/HPF (P < 0.05) in the MI zone at 4 days. Long-term treatment reduced the scar collagen (MI: 70.50 ± 2.35% and MI + losartan: 57.50 ± 2.48, P < 0.05), determined the persistency of RAM 11-positive macro- phages (3.02 ± 0.13 cells/HPF) and CD45 RO-positive lymphocytes (2.77 ± 0.58 cells/HPF, P < 0.05 vs. MI), and reduced the scar thinning ratio at 35 days (P < 0.05). Consequently, the temporal expressions of cardiac AT1R and ANG II post-MI in rabbits are different from those described in other species. Long-term treatment unfavorably modified post-MI remodeling, whereas midterm treatment attenuated this harmful effect. The delay in wound healing (early reduction and late persistency of inflammatory infiltrate) and adverse remodeling observed in long-term-treated animals might explain the unfavorable effect observed in rabbits. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 03636135
- Volume :
- 297
- Issue :
- 1
- Database :
- Academic Search Index
- Journal :
- American Journal of Physiology: Heart & Circulatory Physiology
- Publication Type :
- Academic Journal
- Accession number :
- 43449591
- Full Text :
- https://doi.org/10.1152/ajpheart.00498.2007