TY - JOUR
T1 - Rats exhibit aldosterone-dependent sodium appetite during 24 h hindlimb unloading
AU - Sullivan, Margaret J.
AU - Hasser, Eileen M.
AU - Moffitt, Julia A.
AU - Bruno, Stacy B.
AU - Cunningham, J. Thomas
PY - 2004/6/1
Y1 - 2004/6/1
N2 - Hindlimb unloading (HU) is an animal model of microgravity and bed rest. In these studies, we examined the role of ingestive behaviours in regulating body fluid balance during 24 h HU. In the first experiment, all rats were given distilled water to drink while two groups were also given access to a sodium chloride solution (0.9% or 1.8%). Water and saline intakes were measured before, during and after 24 h of HU. Rats reduced water intake during 24 h HU in all conditions. During HU, rats increased their intakes of both saline solutions (0.9% NaCl (n = 11): control 7.8 ± 3 ml; HU 18.2 ± 4 ml; recovery 8.9 ± 2.5 ml; 1.8% NaCl (n = 7): control 1.0 ± 0.4 ml; HU 3.8 ± 0.3 ml; recovery 1.2 ± 0.5 ml). Although water intake decreased there was no reduction in total fluid intake when saline was available. Plasma volumes were reduced during HU compared to rats in a normal posture when only water was available to drink (control (n = 11) versus HU (n = 11): 4.0 ± 0.2 versus 3.4 ± 0.2 ml (100 g bodyweight)-1). When 0.9% saline was available in addition to water, plasma volumes after 24 h HU were not different from rats in a normal posture (control (n = 11) versus HU (n = 12): 4.3 ± 0.4 versus 4.3 ± 0.1 ml (100 g body weight)-1). Plasma aldosterone but not plasma renin activity was significantly elevated after 24 h HU. Central infusions of spironolactone blocked the increased intake of 1.8% saline that was associated with 24 h HU. Thus, HU results in an aldosterone-dependent sodium appetite and the ingestion of sodium may help maintain plasma volume.
AB - Hindlimb unloading (HU) is an animal model of microgravity and bed rest. In these studies, we examined the role of ingestive behaviours in regulating body fluid balance during 24 h HU. In the first experiment, all rats were given distilled water to drink while two groups were also given access to a sodium chloride solution (0.9% or 1.8%). Water and saline intakes were measured before, during and after 24 h of HU. Rats reduced water intake during 24 h HU in all conditions. During HU, rats increased their intakes of both saline solutions (0.9% NaCl (n = 11): control 7.8 ± 3 ml; HU 18.2 ± 4 ml; recovery 8.9 ± 2.5 ml; 1.8% NaCl (n = 7): control 1.0 ± 0.4 ml; HU 3.8 ± 0.3 ml; recovery 1.2 ± 0.5 ml). Although water intake decreased there was no reduction in total fluid intake when saline was available. Plasma volumes were reduced during HU compared to rats in a normal posture when only water was available to drink (control (n = 11) versus HU (n = 11): 4.0 ± 0.2 versus 3.4 ± 0.2 ml (100 g bodyweight)-1). When 0.9% saline was available in addition to water, plasma volumes after 24 h HU were not different from rats in a normal posture (control (n = 11) versus HU (n = 12): 4.3 ± 0.4 versus 4.3 ± 0.1 ml (100 g body weight)-1). Plasma aldosterone but not plasma renin activity was significantly elevated after 24 h HU. Central infusions of spironolactone blocked the increased intake of 1.8% saline that was associated with 24 h HU. Thus, HU results in an aldosterone-dependent sodium appetite and the ingestion of sodium may help maintain plasma volume.
UR - http://www.scopus.com/inward/record.url?scp=3042542841&partnerID=8YFLogxK
U2 - 10.1113/jphysiol.2004.062265
DO - 10.1113/jphysiol.2004.062265
M3 - Article
C2 - 15047775
AN - SCOPUS:3042542841
SN - 0022-3751
VL - 557
SP - 661
EP - 670
JO - Journal of Physiology
JF - Journal of Physiology
IS - 2
ER -