van Berge-Landry Helene, James Gary D
Department of Anthropology, Binghamton University, Binghamton, New York 13902, USA.
Ann Hum Biol. 2004 Jul-Aug;31(4):477-87. doi: 10.1080/03014460412331281746.
The purpose of this study was to assess, in borderline hypertensive subjects, the homeostatic and allostatic responses of serum electrolytes, proteins, lipids, hematocrit and renal function to an extreme dietary sodium challenge, and to evaluate whether the responses in these clinical parameters were associated with a concomitant response in blood pressure.
Data from middle-aged adults with a diagnosis of mild, uncomplicated borderline hypertension were collected at the end of 1-month randomized trials of low (24 +/- 13 mmol/day) and high (309 +/- 88 mmol/day) dietary sodium intake. A total of 48 subjects (38 men and 10 women) were examined.
Serum sodium increased (p < 0.001), while all other serum electrolytes, except chloride, decreased (p < 0.01) from the low to high sodium diets. Serum proteins (p < 0.05) and hematocit (p < 0.001) also declined among subjects on a high sodium diet. However, creatinine clearance (an indicator of glomerular filtration) increased with sodium intake (p = 0.004). None of these biochemical or renal functional responses was associated with a change in blood pressure.
There are modest yet significant changes in serum electrolytes associated with changes in dietary sodium intake, suggesting that these ions are under an allostatic control mechanism. Serum proteins also appear to function as allostatic compensatory mechanisms, offsetting the net effect of increased serum salinity. It is speculated that the adaptive allostatic renal response to a high sodium diet (an increase in GFR) may result in loss of the ability to appropriately vary renal filtration if that diet is chronically maintained.
