The Role of Chloride in
Deoxycorticosterone Hypertension: Selective Sodium Loading by
Diet or Drinking Fluid
J. KUNEŠ, J. ZICHA, J. JELÍNEK
Center for Experimental Cardiovascular Research, and Institute
of Physiology, Academy of Sciences of the Czech Republic,
Prague, Czech Republic
Received August 20, 2003
Accepted October 24, 2003
Summary
To evaluate the role of chloride in the pathogenesis of
salt-dependent deoxycorticosterone (DOC) hypertension, we
studied young Wistar rats chronically loaded with sodium
bicarbonate (NaHCO3) or sodium chloride (NaCl) which were
administered either in the diet or in the drinking fluid.
Selective sodium loading (without chloride) increased blood
pressure (BP) in DOC-treated animals only if NaHCO3 was provided
in the diet. In contrast, no significant blood pressure changes
were induced by DOC treatment in rats drinking NaHCO3 solution.
Hypernatremia and high plasma osmolality occurred only in rats
drinking NaCl or NaHCO3 solutions. Compared to great volume
expansion in NaCl-loaded DOC-treated rats, the degree of
extracellular fluid volume expansion (namely of its interstitial
fraction) was substantially lower in both NaHCO3-loaded groups
in which significant hypokalemia was observed. NaHCO3-drinking
rats without significant blood pressure response to DOC
treatment represented the only experimental group in which blood
volume was not expanded. In conclusion, our data confirm
previous observations that NaHCO3 loading is less potent in
eliciting DOC hypertension than NaCl loading, but blood pressure
rise in rats fed NaHCO3 diet clearly demonstrated that selective
sodium loading could potentiate the development of DOC
hypertension if NaHCO3 is offered within the appropriate dietary
regimen. The reasons for the failure of NaHCO3-drinking rats to
elevate blood pressure in response to chronic mineralocorticoid
treatment are not obvious. However, the absence of a significant
plasma volume expansion together with hypernatremia and
increased plasma osmolality suggest a considerable degree of
dehydration in these animals which fail to increase their fluid
consumption compared to water drinking rats.
Key words
Sodium • Chloride • Bicarbonate • Blood pressure • Body fluids •
Blood volume
|