Abstract 226: Thyroid Hormone Stimulated Arteriolar Growth Along With Myocyte Hypertrophy Following Myocardial Infarction In Rats

Background Thyroid hormones (THs) have been shown to improve LV function and remodeling in animals post-MI and in the human setting, as well as induce capillary and arteriolar growth in the hypertrophic heart. Whether THs can improve arteriolar growth in the infarcted heart is unknown. Methods MI was produced by ligation of the LAD in female SD rats. Rats were divided into the following groups: (1) Sham MI, (2) MI, and (3) MI+T4 treatment (T4 pellet 3.3mg, 60 days release, implanted subcutaneously immediately following MI). Each group was further divided into two subgroups (n=9 per subgroup) for myocytes isolation and whole heart tissues collection eight weeks after surgery. Isolated myocyte shape and arteriolar density in the non-infarcted area were measured at terminal study. Results T4 treatment improved LV ±dp/dt, normalized TAU, and increased myocyte cross-sectional area without further increasing myocyte length in MI rats. T4 treatment tended to increase the total length of smaller arterioles (5 to 15 μm) proportional to LV weight increase. Conclusions These results suggest that long-term T4 treatment after MI has beneficial effects on myocyte and arteriolar remodeling in the non-infarcted area.