Plasma renin, plasma aldosterone and exchangeable sodium in normotensive and hypertensive kidney transplant recipients with and without transplant renal artery stenosis.

Blood pressure (BP), plasma renin concentration (PRC), plasma aldosterone concentration (PAC) and exchangeable sodium (ES) were studied in 19 kidney recipients on different fixed levels of sodium intake after successful kidney transplantation. The following groups of kidney recipients were investigated: group 1: 7 normotensives, group 2:7 hypertensives without transplant renal artery stenosis (TRAS), group 3:5 hypertensives with angiographically verified TRAS. Hypertension in the recipients without TRAS (group 2) was characterized by a positive correlation between BP and ES and a normal response of PRC and PAC to a fixed low (10 mEQ/day) and high (150 mEq/day) sodium intake. In contrast, hypertension in the recipients with TRAS (group 3) was characterized by a normal or varyingly increased PRC on a liberal sodium intake and a reduced response of PRC to sodium restriction, whereas PAC did not differ from the other groups of recipients. In one recipient in group 3 who underwent surgical correction for TRAS, PRC and PAC decreased before operation during sodium restriction, but BP remained high until after operation, when it normalized simultaneously with a decrease in ES. The results indicate that sodium retention is involved in the pathogenesis of posttransplant hypertension and suggest that an increased activity of the renin--angiotensin system is counterbalanced by an accumulation of sodium in TRAS.