Effects of light saline loading on renal renin and catecholamine release in hypertensive humans

In 8 essential hypertensive patients infusion of 7.5 ml kg-1 b.w. of isotonic saline over 20 min decreased plasma renin activity but did not affect plasma adrenaline or noradrenaline concentrations in suprarenal aortic, renal venous and caval blood. Mean blood pressures and heart rates were unchanged throughout the saline infusion period, whereas the hematocrit was significantly decreased. These data suggest that inhibition of renin secretion after slight volume expansion with saline in hypertensive humans occurs without parallel inhibition of either renal neurosympathetic drive or humoral adrenergic tone to the kidney through circulating catecholamines.