Essential hypertension: inborn error of sodium metabolism?

Salt-induced Hypertension in Rats The history of NaCl-induced hypertension in rats is given iby Meneely and 'Dahl (1961). In our laboratory iwe now have two strains of white Sprague-Dawley rats, both with fairly predictable prognosis relative to the development of hypertension, (Dahl, Heine and Tassinari, 1962). They are called R (for Resistant) and S (for Sensitive), and if chronically fed the same 'balanced diet, low in sodium (0.37% as NaCl) their blood pressure (BP) will differ in that while most members of strain S will have a "normal" systolic BP (less than 140 mm. Hg.), the average will be high relative to that of comparable R animals. Among the few S animals that develop 'hypertension on a low NaCl diet, blood pressures are only moderately elevated and the course is invariably benign. However, if more NaCl is added to the same basic diet, this difference in BP between strains is amplified. All members of S ultimately will become manifestly hypertensive while the BP of -the R-rats is hardly affected, and even moderate hypertension in individuals is uncommon. The rate and 'the degree of BPincrease as well as the malignancy of disease afflicting S-members depend on the amount of salt added and the age at which it is started. The heavier the exposure, and the earlier in life it 'begins, the more malignant the disease. If -these animals are placed on a diet containing 8% NaCl immediately after weaning at 3 weeks of age, they will all rapidly develop hypertension and most will be dead or dying