Blood pressure and hormonal changes following alteration in dietary sodium and potassium in young men with and without a familial predisposition to hypertension

The blood pressures (BP) of the parents of a group of students were determined and two subgroups of students were defined, one with (PHT group) and one without (PNT group) a familial predisposition to hypertension. Observations were made in both groups during three periods of modified dietary electrolyte intake: (i) no-added sodium (low Na), (ii) no added sodium with potassium supplementation (low Na/high K), and (iii) sodium supplementation (high Na). The diets were given in random order. At the start of the trial, while the students continued their customary diet, the PHT group had higher systolic and diastolic pressures and plasma noradrenaline levels than the PNT group. At the end of 4 weeks of the high Na diet, the BP levels of both groups were significantly higher than those after the low Na diet. In contrast, when the low Na diet was supplemented for 2 weeks with potassium, BPs of the PHT group fell significantly, while those of the PNT group rose slightly. BP in the PHT group was significantly lower during the low Na/high K than during the high Na diet (systolic 10.5 mm Hg +/- 2.3 SE; diastolic 11.2 +/- 2.5, the changes being significantly different from those in the PNT group. The changes in plasma renin and aldosterone were similar in both groups during the different diets. Plasma noradrenaline fell in the PHT group, but rose in the PNT group when the low Na diet was supplemented with potassium. This fall in plasma noradrenaline in the PHT group during the low Na/high K diet correlated with the falls in systolic and diastolic BP. It is concluded that whereas young adults with a familial predisposition to hypertension behave similarly to those without such a predisposition in having a pressor response to a high sodium intake, they are peculiar in showing a depressor response to a high potassium intake.