Alterations in vascular alpha and beta adrenergic responsiveness in the Dahl rat: a preliminary report

The effect of a high salt diet on in vitro vascular adrenergic responsiveness of Dahl salt-sensitive (DS) and salt-resistant (DR) rats was investigated. Female DS and DR rats were fed either a normal (low salt) or high salt (8%) diet for 7 weeks. DS rats on the high salt diet showed a progressive increase in systolic blood pressure (SBP) and were considered hypertensive (SBP greater than 150 mmHg) at the time of experimentation. SBP did not change appreciably in either the DS rats on a low salt diet or in the DR rats on either diet. Isoproterenol induced relaxation of rings of aortic smooth muscle from DS rats on the high salt diet was significantly attenuated when compared to the other three groups. However, relaxation in response to sodium nitrite was similar in the 4 groups. An enhanced aortic smooth muscle response to norepinephrine stimulation was observed in both the DS and DR rats maintained on the high salt diet, whereas no difference was seen in the contractile response to KC1 depolarization. In contrast to previous reports, the present study shows that alterations do occur in in vitro vascular adrenergic responsiveness of the Dahl rat.