'Calcium agonist' in salt-dependent hypertension: hints at calcium-mediated blood pressure increase.

To substantiate further the hypothesized importance of increased calcium influx into vascular smooth muscle, salt-sensitive Dahl rats (DS/JR, John Rapp), on either a low or a high salt diet, were treated with 100 or 300 ppm (i.e. mg/kg food) BAY k 8644, a calcium agonist. Simultaneously, salt-resistant Dahl rats (DR/JR) on a high salt diet received 300 ppm BAY k 8644. Blood pressure rose more rapidly in the agonist-treated DS/JR rats than in the untreated DS/JR controls on high salt diet. On the low salt diet, blood pressure was only slightly higher in the agonist-treated DS/JR. Although an increased calcium influx seems to be involved in salt-induced hypertension, the presence of high sodium chloride is apparently essential for its development. In addition, since DR/JR rats remained resistant to the effect of the calcium agonist, calcium per se is not the decisive factor responsible for the sensitivity or resistance of Dahl rats to salt load.