Abstract
Renin-angiotensin system (RAS) presents a close relation to thyroid hormone levels, but little is known about cardiac RAS in hypothyroidism. We investigated the effect of hypothyroidism on cardiac angiotensin II (Ang II) levels and its receptor expression. Methods Adult male Wistar rats were divided in Control and Hypothyroid (Hypo). Hypo were thyroidectomized and treated with 0.05% methimazole added to their drinking water during 14 days. On the 15th day, animals were decapitated, heart was removed and weighed. Systolic blood pressure (SBP) and heart rate (HR), cardiac and plasmatic Ang II levels and hormone measurements in serum were assayed. ANF, Ang II type 1 and type 2 receptor expression were determinated by RT-PCR and Western-Blott. Results Serum T3 and T4 levels confirmed their hypothyroid state. SBP and HR decreased in Hypo rats when compared to control. ANF mRNA expression were also lower than control. No change was observed in Ang II levels. AT1 gene expression in Hypo was increased compared to control (313.73% „b 53.71% vs 100%, p<0.05) as well protein levels (23.25%). mRNA and protein AT2 receptor were also increased in Hypo (517.02% and 37.10%, respectively, p<0.05). Conclusion The present study showed that although the thyroid hormone privation did not alter plasma or cardiac Ang II, the sensibility of cardiac tissue to Ang II is increased in this state. Financial support: FAPESP.
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