Are all individuals equally sensitive in the blood pressure to high salt intake? (Review article)

It has been reported that only one-third of normotensive subjects and half of hypertensive patients are salt-sensitive. Many causes of salt-sensitivity have been proposed. Our suggestion is that a reduced urinary kallikrein level may be one cause, since mutant kininogen-deficient rats, which cannot generate kinin in the urine, are salt-sensitive. Renal kallikrein is secreted by the connecting tubule cells of the kidney, which are located just distal to the macula densa or the tubuloglomerular feedback system. Excess amounts of sodium taken overflow into the distal tubules and are reabsorbed in the collecting ducts. Kinins generated inhibit sodium reabsorption in the collecting ducts. Both blacks and whites with essential hypertension excrete less urinary kallikrein than do their normotensive counterparts, but the mean value in "normotensive blacks" were not different from that in "hypertensive whites". African-Americans consume less potassium than whites. Potassium and ATP-sensitive potassium channel blockers are releasers of renal kallikrein. In a small-scale study, sodium loading caused more increase in the systolic blood pressure in urinary low-kallikrein group than in urinary high-kallikrein group. Large-scale clinical studies, under strict control of potassium intake, are needed to elucidate the relationship between salt-sensitivity and urinary kallikrein levels.