Role of Peripheral Adrenergic Responsiveness in the Development of DOCA/NaCl Hypertension in Rats

Alterations in α- and β-adrenergic responsiveness were investigated prior to and during the development of hypertension in rats treated with desoxycorticosterone acetate and NaCl (DOCA/ NaCl). The DOCA/NaCl rats became noticeably hypertensive (> 150 mm Hg) six weeks after the initiation of treatment. Prior to the development of hypertension, a reduced in vivo and in vitro β- and an enhanced α-adrenergic responsiveness of the DOCA/NaCl group resulted. At 2 and 12 weeks of the study, the dipsogenic response to isoproterenol was significantly attenuated in the DOCA/NaCl rats, whereas no difference in the dipsogenic response to 24 hour water deprivation was observed between control and DOCA/NaCl rats. Isoproterenol-induced relaxation of aortic smooth muscle from the DOCA/NaCl treated rats was significantly reduced at 4 weeks and further attenuated at 12 weeks of the study. However, aortic smooth muscle sensitivity to norepinephrine stimulation was significantly increased at 4 and 12 weeks of the study. These results suggest that alterations in both in vivo and in vitro α- and β-adrenergic responsiveness occur prior to establishment of hypertension of the DOCA/NaCl rats and that these alterations may have a role in the early stages of the development of this form of hypertension.