TY - JOUR
T1 - Endocrine responses during exercise-heat stress
T2 - Effects of prior isotonic and hypotonic intravenous rehydration
AU - Castellani, John W.
AU - Maresh, Carl M.
AU - Armstrong, Lawrence E.
AU - Kenefick, Robert W.
AU - Riebe, Deborah
AU - Echegaray, Marcos
AU - Kavouras, Stavros
AU - Castracane, V. Daniel
N1 - Funding Information:
Acknowledgements The authors thank Mike Whittlesey, Douglas Casa, Dane McFarland, Dean Aresco, Nicole Johnson, and Marie Kenefick (University of Connecticut) and Terry Gimpel (Texas Tech University) for their technical support. We also thank our subjects for their participation. This work was supported in part by the Proctor and Gamble Company and a grant from the University of Connecticut Research Foundation.
PY - 1998/2
Y1 - 1998/2
N2 - Exercise following exercise-induced dehydration (EID) has been shown to elevate concentrations of plasma norepinephrine (NE) and hypothalamic-pituitary-adrenal axis hormones. However, it is not known how intravenous (i.v.) rehydration (Rh) with isotonic (ISO) or hypotonic (HYPO) saline affects these hormone concentrations. It was hypothesized that HYPO, versus ISO, would lead to lower plasma NE and cortisol concentrations ([CORT]) during subsequent exercise following EID due to a decrease in plasma sodium concentration [Na+]. Eight non-heat acclimated men completed three experimental treatments (counterbalanced design) immediately following EID (33°C) to -4% body mass loss. The Rh treatments were i.v. 0.9% NaCl (ISO, 25 ml.kg-1), i.v. 0.45% NaCl (HYPO, 25 ml.kg-1), and no fluid (NF). After Rh and rest (2 h total), the subjects walked at 53-54 percent of maximal O2 uptake for 45 min at 36°C. After Rh, the following observations were made before/during exercise: percentage change in plasma volume (PV) was lower in NF compared to ISO and HYPO but similar between ISO and HYPO; Δ [Na+] was similar between ISO and NF and higher in ISO compared to HYPO; Δ plasma NE was higher in NF compared to ISO and HYPO, but similar between ISO and HYPO; Δ plasma [CORT] was higher in NF compared to ISO and HYPO and higher in ISO compared to HYPO; rectal temperature was higher in NF compared to ISO and HYPO. These data would suggest that sympathetic nervous activity and [CORT] during exercise, subsequent to EID and Rh, was affected by lower PV (probably through cardiopulmonary baroreflexes) as well as core temperature. Furthermore, [CORT] was affected by Δ [Na+] after Rh through an unknown mechanism.
AB - Exercise following exercise-induced dehydration (EID) has been shown to elevate concentrations of plasma norepinephrine (NE) and hypothalamic-pituitary-adrenal axis hormones. However, it is not known how intravenous (i.v.) rehydration (Rh) with isotonic (ISO) or hypotonic (HYPO) saline affects these hormone concentrations. It was hypothesized that HYPO, versus ISO, would lead to lower plasma NE and cortisol concentrations ([CORT]) during subsequent exercise following EID due to a decrease in plasma sodium concentration [Na+]. Eight non-heat acclimated men completed three experimental treatments (counterbalanced design) immediately following EID (33°C) to -4% body mass loss. The Rh treatments were i.v. 0.9% NaCl (ISO, 25 ml.kg-1), i.v. 0.45% NaCl (HYPO, 25 ml.kg-1), and no fluid (NF). After Rh and rest (2 h total), the subjects walked at 53-54 percent of maximal O2 uptake for 45 min at 36°C. After Rh, the following observations were made before/during exercise: percentage change in plasma volume (PV) was lower in NF compared to ISO and HYPO but similar between ISO and HYPO; Δ [Na+] was similar between ISO and NF and higher in ISO compared to HYPO; Δ plasma NE was higher in NF compared to ISO and HYPO, but similar between ISO and HYPO; Δ plasma [CORT] was higher in NF compared to ISO and HYPO and higher in ISO compared to HYPO; rectal temperature was higher in NF compared to ISO and HYPO. These data would suggest that sympathetic nervous activity and [CORT] during exercise, subsequent to EID and Rh, was affected by lower PV (probably through cardiopulmonary baroreflexes) as well as core temperature. Furthermore, [CORT] was affected by Δ [Na+] after Rh through an unknown mechanism.
KW - Plasma adrenocorticotropic hormone
KW - Plasma cortisol
KW - Plasma norepinephrine
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U2 - 10.1007/s004210050328
DO - 10.1007/s004210050328
M3 - Article
C2 - 9535585
AN - SCOPUS:0031884279
SN - 1439-6319
VL - 77
SP - 242
EP - 248
JO - European Journal of Applied Physiology
JF - European Journal of Applied Physiology
IS - 3
ER -