Gene Expression of Adrenoceptors in the Hearts of Cold-Acclimated Rats Exposed to a Novel Stressor
Changes in the heart rate and force of contraction are regulated by catecholamines via adrenoceptors (AR). In this work, we measured gene expression of AR in left heart atria and ventricles in rats exposed to cold stress and in cold-acclimated rats exposed to a novel stressor (immobilization). We found a significant increase in ?3-AR in left ventricle of rats exposed to acute (1 day) and long-term (28 days) cold, but no changes in ?1- and ?2-AR mRNA levels. However, single immobilization significantly decreased ?2-AR mRNA levels both in left atria and ventricles compared to acute cold stress. Application of a novel stressor (immobilization) to previously cold-acclimated animals did not show decrease of ?2-AR mRNA levels as seen in intact animals. Moreover, ?1- and ?2-AR did not show any significant changes. Surprisingly, the most prominent changes in the heart were detected for ?1B-AR gene expression. We found decreased levels of ?1B-AR mRNA in the heart of rats exposed to cold and immobilization. We also found that exposure of cold-acclimated rats to immobilization is responsible for additional decrease of ?1B-AR mRNA levels in heart. It seems that while ?-AR undergoes adaptation, ?1B-AR is probably prepared to modulate heart functions. Proposed mechanism of ?-AR adaptation needs to be elucidated. Thus, we have shown that gene expression of different AR subtypes in the heart is regulated differently by various stressors. A protective role of ?2-, ?3-AR, and ?1B-AR in the process of heart adaptation to chronic stress exposure is proposed.
gene expression adrenoceptors heart cold immobilization