Dihydropyridine calcium antagonists and agonists in the isolated perfused Dahl rat kidney

Isolated perfused kidneys from prehypertensive Dahl salt-sensitive (DS) rats demonstrated marginally increased glomerular responsiveness when nitrendipine or verapamil was superimposed upon norepinephrine vasoconstriction. This was manifested by a greater increase in the glomerular filtration rate of DS rat kidneys, as compared to kidneys from Dahl salt-resistant (DR) rats. This glomerular response to nitrendipine by isolated kidneys was not affected by the development of salt-induced hypertension in DS rats, but was eliminated by antecedent salt loading in DR rats. In further experiments designed to assess more directly the reactivity of renal vascular calcium channels in DS and DR rats, the calcium channel agonist BAY-K-8644 and its pure agonist isomer elicited greater increases in renal vascular resistance in kidneys from prehypertensive DS rats than in kidneys from similarly prepared DR rats. Renal vascular reactivity to both BAY-K-8644 and its agonist isomer were greatly magnified following salt-induced DS rat hypertension. These results suggest that a genetically conferred abnormality of calcium channel function may contribute to the renal functional characteristics of the DS rat kidney.