Sodium sensitivity of blood pressure in hypertensives is not related to sodium, but rather to renin.
OBJECTIVE
To investigate whether a certain degree of sodium-sensitivity of blood pressure (BP) in essential hypertensives during sodium restriction is related to cumulative sodium loss.


METHODS
One-hundred and seventeen untreated essential hypertensives were admitted to a metabolic ward for 7 days and put on a sodium restricted diet of 55 mmol/day. During these 7 days urinary excretions of sodium, potassium and creatinine were determined daily along with mean arterial pressure (MAP) and weight. Active plasma renin concentration (APRC), aldosterone (ALDO), renal plasma flow (RPF) and plasma volume (PV) were assessed after 7 days under steady state condition. The population was divided into tertiles based on the final changes in BP after 7 days.


RESULTS
Textile 1 displayed a median fall in MAP of -13 (-42 to -9) mm Hg, whereas in tertile 2 and 3 a fall of -6 (-9 to -4) mm Hg and a rise of +1 (-3 to +11) mm Hg respectively, was encountered. Baseline characteristics were comparable between the tertiles. When tertile 1 was compared to tertile 3 no significant differences between these tertiles were found with respect to cumulative sodium and potassium balances and weight loss. Furthermore, APRC levels were significantly higher in tertile 3 as compared to tertile 1 (22 and 27 mU/l, respectively). Renal vascular resistance (RVR) tended to be higher in tertile 3, although this was not statistically significant. Aldo, RPF and PV were comparable between the tertiles.


CONCLUSIONS
In contrast with tertile 1, MAP in tertile 3 is maintained at its original level, despite comparable sodium losses. In tertile 3, however, levels of renin are higher compared to the group that is more sodium-sensitive. Therefore, our data suggest that the degree of sodium-sensitivity of BP in essential hypertensive subjects is not determined by sodium status, but rather by renin.
Krekels
M M
MM
Department of Medicine, University Hospital Maastricht, The Netherlands.
van Es
P N
PN
Leunissen
K M
KM
De Leeuw
P W
PW
D000293:Adolescent; D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000187:drug effects*; D006439:Hemodynamics; D006706:Homeostasis; D006728:Hormones / Q000097:blood; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008875:Middle Aged; D009318:Natriuresis; D011188:Potassium / Q000097:blood; D012079:Renal Circulation; D012083:Renin / Q000097:blood*; D012964:Sodium / Q000494:pharmacology*; D015431:Weight Loss
D006728:Hormones; D012964:Sodium; D012083:Renin; D011188:Potassium