Increased vascular response to calcium channel agonist by Dahl S rat kidney

We examined responses to the calcium channel agonist, BAY-K 8644, of isolated perfused kidneys from Dahl salt-sensitive (DS) and -resistant (DR) rats that had been stabilized on high (HI) and low (LO) NaCl intakes. Mean arterial pressures of DS/HI rats exceeded those of the other three groups. BAY-K 8644 significantly increased the renal vascular resistance (RVR) of DS/HI and DS/LO kidneys, by 38 and 12%, respectively, but did not increase RVR of DR/HI or DR/LO kidneys significantly (6 and 2%, respectively). Increases in RVR and decreases in glomerular filtration rate of DS/HI kidneys exceeded those of DR/HI kidneys. Increases in the RVR of DS/LO kidneys exceeded those of DR/LO kidneys. Experiments utilizing the separate calcium channel agonist and antagonist enantiomers of BAY-K 8644 corroborated these findings, but at lower concentrations. "Chemical sympathectomy" with 6-hydroxydopamine increased the reactivity of kidneys from only high-NaCl animals to BAY-K 8644 without regard to Dahl S or R status. In conclusion, the DS kidney vasculature manifests an increase in responsiveness to this calcium channel agonist, independently of antecedent NaCl loading or high blood pressure. However, a high antecedent salt intake or hypertension enhances vascular responsiveness of the DS kidney to BAY-K 8644.