Extrarenal Na+ balance, volume, and blood pressure homeostasis in intact and ovariectomized deoxycorticosterone-acetate salt rats.
Water-free Na+ storage may buffer extracellular volume and mean arterial pressure (MAP) in spite of Na+ retention. We studied the relationship among internal Na+, K+, water balance, and MAP in Sprague-Dawley rats, with or without deoxycorticosterone-acetate (DOCA) salt, with or without ovariectomy (OVX). The rats were fed a low-salt (0.1% NaCl) or high-salt (8% NaCl) diet for 5 weeks. DOCA salt increased MAP (161+/-14 versus 123+/-4 mm Hg; P<0.05), and DOCA-OVX salt increased MAP further (181+/-22 mm Hg; P<0.05). DOCA salt increased the total body Na+ by &40% to 45%; however, water-free Na+ retention by osmotically inactive Na+ storage and by osmotically neutral Na+/K+ exchange allowed the rats to maintain the extracellular volume close to normal. DOCA-OVX salt rats showed similar Na+ retention. However, their osmotically inactive Na+ storage capacity was greatly reduced and only partially compensated by neutral Na+/K+ exchange, resulting in greater volume retention despite similar Na+ retention. For every 1% wet weight total body water gain, MAP increased by 2.3+/-0.2 mm Hg in DOCA salt rats and 2.5+/-0.3 mm Hg in DOCA-OVX salt rats. Because water-free Na+ retention buffered total body water content by 8% to 11% wet weight, we conclude that this internal Na+ escape buffered MAP. Extrarenal Na+ and volume balance seem to play an important role in long-term volume and MAP control.
Titze
Jens
J
Department of Nephrology and Hypertension, Friedrich-Alexander-University, Erlangen-Nürnberg, Germany. jens.titze@rzmail.uni-erlangen.de
Luft
Friedrich C
FC
Bauer
Katharina
K
Dietsch
Peter
P
Lang
Rainer
R
Veelken
Roland
R
Wagner
Hubertus
H
Eckardt
Kai-Uwe
KU
Hilgers
Karl F
KF
D000818:Animals; D001794:Blood Pressure; D003900:Desoxycorticosterone; D045604:Extracellular Fluid / Q000378:metabolism*; D005260:Female; D006706:Homeostasis; D006973:Hypertension / Q000139:chemically induced* / Q000503:physiopathology; D010052:Ovariectomy; D011188:Potassium / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism*; D012965:Sodium Chloride; D014882:Water-Electrolyte Balance
D003900:Desoxycorticosterone; D012965:Sodium Chloride; D012964:Sodium; D011188:Potassium