Objective: To investigate the effect of benazepril on atrial cytoskeleton remodeling in atrial fibrillation (AF) canines induced by chronic rapid atrial pacing (RAP).
Methods: Twenty canines were randomly divided into 3 groups: (1) Sham-operated group without RAP; (2) AF group: AF established by RAP at 600 beats per minute for 6 weeks; (3) Benazepril group: benazepril was dosed from 1 week pre-pacing to 6 weeks post-pacing. The diameter of atrial cardiomyocyte was measured, collagen volume fraction (CVF) analyzed by Masson staining and the expression and distribution of desmin were assayed by immunohistochemistry. RT-PCR method was used to semi-quantify the mRNA expression of beta-tubulin and desmin.
Results: The diameter of atrial cardiomyocyte increased in AF group [LA:(27.9 +/- 3.8) microm; RA: (26.8 +/- 3.2) microm] and benazepril group[LA: (25.1 +/- 3.4) microm; RA: (25.2 +/- 3.5) microm] than sham-operated group [LA: (19.6 +/- 2.9) microm; RA: (18.7 +/- 2.6) microm] (P < 0.01). CVF increased in AF group than sham-operated group [LA: (16.9 +/- 1.1)% vs (9.2 +/- 0.9)%, RA: (15.7 +/- 2.3)% vs (9.3 +/- 0.8)%, P < 0.01] and it decreased in benazepril group than AF group [LA: (11.3 +/- 0.8)% vs (16.9 +/- 1.1)%, RA: (10.9 +/- 0.8)% vs (15.7 +/- 2.3)%, P < 0.01]. Normal desmin cross-striations were lost in atrial cardiomyocyte and the desmin organization became irregular in AF group. The A values analyzed by immunohistochemistry of desmin increased in AF group than sham-operated group and they decreased in benazepril group than AF group (P < 0.01). The expression of mRNA level of desmin and beta-tubulin were up-regulated in AF group than sham-operated group, (LA:1.0 +/- 0.3 vs 0.6 +/- 0.3, 0.9 +/- 0.4 vs 0.6 +/- 0.3; RA: 1.0 +/- 0.6 vs 0.6 +/- 0.2, 1.1 +/- 0.3 vs 0.7 +/- 0.4, P < 0.01) and they were down-regulated in benazepril group than AF group (LA:0.8 +/- 0.4 vs 1.0 +/- 0.3, 0.7 +/- 0.3 vs 0.9 +/- 0.4; RA:0.7 +/- 0.3 vs 1.0 +/- 0.6, 0.7 +/- 0.3 vs 1.1 +/- 0.3, P < 0.01).
Conclusion: Benazepril can favorably improve atrial cytoskeleton remodeling in the canine atrial fibrillation model.