The influence of different sodium loads on renin release in hypertensive and normotensive states of chronic renal failure

Abstract

The purpose of the present study was to examine the influence of different sodium loads on renin release in the hypertensive and normotensive state of chronic renal failure. Blood pressure (BP), plasma renin concentration (PRC) and exchangeable sodium (Na_E) were measured in eighteen patients with advanced chronic renal failure, nine hypertensives and nine normotensives, and in seven normal subjects (a) 6 days after a fixed sodium intake of 10 mmol/day, and (b) 6 days after a fixed sodium intake of 150 mmol/day. Mean Na_E was 14–19% higher in the hypertensives compared with the normotensives and values of Na_E correlated significantly to values of mean BP. No significant differences were present in PRC between the groups of patients and controls on either of the sodium regimens and no correlation was found between BP and PRC. However, average decreases of PRC in the hypertensives on high sodium intake, 33–34%, were significantly lower than the corresponding values of 69–71% in the normotensive patients and controls, respectively. Furthermore, the percentage changes of PRC on high sodium intake correlated significantly to mean BP as well as to Na_E. These results suggest that renin release is relatively unresponsive to different sodium intakes in hypertension following chronic renal failure. This alteration in renin release may contribute to the maintenance of hypertension in chronic renal failure, PRC being ‘inappropriately’ increased in relationship to the sodium excess.

Key Words:

• chronic renal failure
• hypertension
• plasma renin concentration
• sodium