BETA-ADRENOCEPTOR RESPONSIVENESS OF SPLENIC MACROPHAGES IN NORMOTENSIVE AND HYPERTENSIVE RATS

The aim of the present study was to investigate putative mechanisms im plicated in the impaired phagocytic response of spontaneously hyperten sive rats (SHR)(1). The effect of in vitro treatment with isoprotereno l (ISO), a beta-adrenergic drug, on phagocytosis and respiratory burst by splenic macrophages (SpM circle divide) from normotensive Wistar-K yoto rats (WKY) and SHR with established hypertension, respectively, w as evaluated. Furthermore, the relaxant effect of ISO was determined i n phenilephrine-precontracted thoracic aorta strips form SHR compared with age-matched WKY rats. Results indicate that exposure of rat SpM c ircle divide to ISO generate a significant and dose-dependent reductio n of phagocytosis and oxidative burst which was antagonized, almost co mpletely, by the beta-adrenergic antagonist propranolol (PRO). Unlike normotensive, in hypertensive rats treatment with ISO fail to modulate phagocytosis and respiratory burst activity by SpM circle divide. At vascular level, aortic relaxation by ISO was reduced in SHR when compa red to WKY rats. These findings suggest that SHR exhibit changes not o nly in vascular, but also in macrophage beta-adrenoceptor-mediated res ponses. It is postulable that sympathetic overactivity could be respon sible for impaired phagocytic functions and beta-receptor alternations observed in SHR.