Increased β2-adrenoreceptor density in heart, kidney and lung of spontaneously hypertensive rats

Abstract

The development of .beta.-adrenoreceptor density and .beta.1- and .beta.2-adrenoreceptor distribution has been investigated in heart, kidney and lung of spontaneously hypertensive (SHR) and normotensive (WKY) rats by (-)125I-iodocyanopindolol binding at the age of 5-6, 9-10 and 19-21 weeks. At all ages .beta.-adrenoreceptor density was similar in hearts of both strains, while it was increased in kidney and lung of SHR compared to WKY. The .beta.2-adrenoreceptor density was higher in all three tissues of SHR at all ages investigated. On the other hand, .beta.1-adrenoreceptor density was decreased in heart, unchanged in lung and increased in kidney of SHR compared to WKY. Destruction of presynaptic nerve terminals by treatment of WKY with 6-hydroxydopamine produced a 24% loss of cardiac .beta.2-adrenoreceptors, whereas the .beta.1-adrenoreceptor density remained unchanged, suggesting that at least part of the cardiac .beta.2-adrenoreceptor population is localized prejunctionally. It is suggested that .beta.2-adrenoreceptor are involved in the development or maintenance of high blood pressure in SHR, possibly by facilitating noradrenaline release.