Changes in the expression and function of beta‐adrenergic receptors subtypes In the rat aorta during development

Abstract

During his life the rat shows changes in the relaxation response mediated by beta adrenergic receptors (βAR). In order to provide additional information on the topic, we studied the changes that may occur in the expression, localization and in vitro function of each subtype βAR in the thoracic aorta of male Wistar rats of two age groups: 3 weeks (prepuberty) and 9 weeks (postpuberty). The results indicate that, after the ninth week, the pretreatment with ICI 118.551 (β2 selective inhibitor, 10‐7 M) but not with CGP 12177 (selective inhibitor of β1, 10‐7 M) inhibited the relaxation response in all groups. However, the inhibition was greater when both antagonists were administered simultaneously. In addition, BRL 37344 (selective β3 agonist) caused relaxation only in prepuberty rats rings, which was blocked by SR 59230A (antagonist β3, 10‐6 M). Consistent with previous data, there was an increase in the expression of β1 and β2 receptors and decreased the β3 from the ninth week rats. Moreover, β1 and β2 subtypes are mainly located in smooth muscle, whereas β3 are located mainly in the endothelium. In conclusion, β1 receptors do not appear to participate functionally by themselves at any age, the β3 only involved in prepuberty rats and β2 are involved in all groups but their affinity is likely to change from the ninth week. Interestingly, the combination of β1 and β2 antagonists produced a synergistic effect which deserves further investigation.