AGE AS A DETERMINANT OF RENAL SODIUM CONSERVATION IN NORMAL MAN

  • 1 January 1976
    • journal article
    • research article
    • Vol. 87  (3) , 411-417
Abstract
Age modifies a number of factors which determine renal Na handling including the rate of glomerular filtration, renal hemodynamics, and the responsiveness of the renin-angiotensin-aldosterone system. This study was carried out to examine the effects of age on the capacity of the normal human kidney to respond to restriction of Na intake. Renal conservation of Na and response to dietary Na restriction was assessed in 89 healthy subjects who were free of cardiovascular, renal or adrenal disease. The daily reduction in urine Na which followed restriction of intake to 10 meq of Na and 100 meq of K/day conformed well to an exponential function, defined by an unweighted least-squares fit. The half-time for the reduction in renal Na excretion in subjects under 30 yr was -17.6 .+-. 0.7 h, significantly faster than for subjects aged 30-59, who had a relatively constant half-time (23.4 .+-. 1.1 h). In subjects over 60 yr of age the half-time was prolonged to 30.9 .+-. 2.8 h, significantly greater than that of the younger age group. These observations indicate that age significantly influences the kidney''s capacity to conserve Na. Age-related change must be considered in the assessment of this function in human disease.