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The role of beta3-adrenoceptors and muscarinic receptors in the response of the heart to stress We have shown previously that not only beta-adrenoceptors participate on response to stress in the lung tissue. The aim of this study was to elucidate the role of other heart receptors: beta3-adrenoceptors (beta3-AR) and muscarinic receptors (MR) in stress response. We studied the effects of cold and immobilization (IMO) stress treatment on the amount of the alpha1, beta1, beta2, beta3-AR, MR binding sites, on the mRNA levels and receptor protein concentrations, on the basal and stimulated adenylyl cyclase activity in specific heart regions (in the left (LV) and right (RV) ventricles) in rat and in mice lacking M2 MR. We used radioligands for receptor binding sites determination. Gene expression was determined using RT-PCR, the amount of respective receptor protein was determined using Western blots. Gene expression of rat beta3-AR was significantly affected by immobilization stress in rat LV, RV. 7 IMO caused the increase in the amount of beta3-AR mRNA in LV and the same trend was observed on protein levels and in the density of beta3-AR binding sites. In RV, there was an increase in the amount of mRNA for beta3-AR, but there were no changes in the protein concentration and in the number of receptor binding sites. On the other hand, 1 IMO induced the increase in the amount of the mRNA for beta3-AR in LV but there was decrease in the quantity of beta3-AR binding sites. Single and repeated cold treatment caused the analogical effects. The activity of adenylyl cyclase was affected by stress as well. The experiments with M2 KO mice showed that M2 MR are not essential for the stress reaction and that beta-AR are important players in stress response. We conclude that beta-AR are mainly important in the heart response to stress in variance to lung. This work was supported by Grant GAUK 11/06 |
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