Differential sensitivity of Dahl salt-sensitive and Dahl salt-resistant rats the hypotensive action of acute nifedipine administration
The calcium antagonist, nifedipine, was intravenously administered in a cumulative fashion, from 0.5 to 12 mg/kg, to Dahl salt-sensitive (DS) and Dahl salt-resistant (DR) rats which had been maintained on a high (8.0%) or low (0.4%) salt (NaCl) diet. We observed, compared with the DR rats, dose-related and significant (P less than 0.001) falls in the systolic (SBP) (72 +/- 3 and 60 +/- 9%, respectively) and diastolic blood pressure (DBP) (67 +/- 2 and 62 +/- 6%) o the DS rats maintained either on the low (0.4%) or high (8.0%) salt diets. In contrast, nifedipine therapy comparatively produced only moderate changes in the SBP and DBP of the DR rats (36 +/- 12, 27 +/- 9, 31 +/- 10, and 30 +/- 11%, respectively). We hypothesize that this differential sensitivity of the DS and DR rats to the hypotensive action of nifedipine may reflect a significantly more important role for a high resting Ca2+ influx, through nifedipine sensitive channels, in the maintenance of the blood pressure of the DS rat.