Evidence for a prolonged biological half-like of Na22 in patients with hypertension.

• In the treatment of human hypertension, the effectiveness of sodium restriction by either dietary means or natriuretic agents is now well established. This response to sodium restriction suggested that hypertensives might suffer from an increase in total body sodium. The first measurements of the sodium content of individuals with hypertension were done, in 1951, by the technique of isotopic dilution using Na-. With the exception of one report,the original observations have been confirmed repeatedly :~° exchangeable sodium in the hypertensive was not increased. In the single discordant report, some cases of severe hypertension were found to have an increase in (exchangeable) sodium, but this was interpreted to be secondary to the disease, rather than primary, because it occurred almost exclusively in individuals with advanced hypertension, presumably with markedly impaired 7enal function. In 1953, it was observed that when the average salt consumption of rats was increased, the mean systolic pressure increased linearly. Humans showed a similar type of correlation : As the average salt consumption of a community increased, the prevalence of hypertension increased linearly. Such observations indicated a fundamental role of salt in the pathogenesis of hypertension. They were interpreted as showing that chronic excess salt consumption plays a primary role in the etiology of human hypertension."' In view of these developments, we were led to reconsider the possibility that there might exist in hypertension some defect in sodium metabolism which was not put into evidence by the earlier isotopic studies. Therefore dur-