POTASSIUM-DEPLETION AND SALT-SENSITIVE HYPERTENSION IN DAHL RATS - EFFECT ON CALCIUM, MAGNESIUM, AND PHOSPHATE EXCRETIONS

Weanling male inbred Dahl rats (Jr salt-sensitive (S) and salt-resista nt (R) strains) were placed on high (4%, HK) and low (0.2%, LK) potass ium diets for 4 weeks. Both diets contained 8% sodium chloride, 2.5% c alcium, 0.8% magnesium, and 2.0% phosphorous. Balance studies were car ried out during the final week on the diets. Mean arterial blood press ure was determined, and dietary intake and urinary output of water, so dium, chloride, potassium, calcium, magnesium, and phosphate were moni tored daily during this period. The data show that blood pressures of S rats were significantly higher than those of R rats on both HK and L K diets; however, reduced dietary potassium was associated with increa sed blood pressure in both strains. Urinary excretions of calcium and magnesium were higher, and urinary phosphate excretion was lower, in S compared to R rats. Decreased potassium intake was associated with in creased excretion of calcium, magnesium and phosphate in both strains. The changes in calcium and magnesium excretion were significantly cor related to blood pressure across strains and diets. We conclude that t he effects of a high salt diet on increasing blood pressure can be pot entiated by lack of potassium, even in previously salt-resistant rats. Increased blood pressure is associated with increased divalent cation excretion. It is not yet known whether this is a cause-and-effect rel ationship.