GENETICALLY-DETERMINED CHLORIDE-SENSITIVE HYPERTENSION AND STROKE

The stroke-prone spontaneously hypertensive rat (SHRSP) is a genetical ly determined model of ''salt-sensitive'' stroke and hypertension whos e full phenotypic expression is said to require a diet high in Na+ and low in K+. We tested the hypothesis that dietary Cl- determines the p henotypic expression of the SHRSP. In the SHRSP fed a normal NaCl diet , supplementing dietary K+ with KCI exacerbated hypertension, whereas supplementing either KHCO3 or potassium citrate (KB/C) attenuated hype rtension, when blood pressure (BP) aas measured radiotelemetrically, d irectly and continually. Supplemental KCI, hut not KB/C, induced strok es, which occurred in all and only those rats in the highest quartiles of both BP and plasma renin activity (PRA). PRA was higher with KCI t han with KB/C. These observations demonstrate that with respect to bot h severity of hypertension and frequency of stroke the phenotypic expr ession of the SHRSP is (i) either increased or decreased, depending on whether the anionic component of the potassium salt supplemented is, or is not, Cl-; (ii) increased by supplementing Cl- without supplement ing Na+, and despite supplementing K+; and hence (iii) both selectivel y Cl--sensitive and Cl--determined. The observations suggest that in t he SHRSP selectively supplemented with CI-the likelihood of stroke dep ends on the extent to which both BP and PRA increase.