AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 2 414-R422, Copyright © 1995 by American Physiological Society
Osmoregulatory modulation of thermal sweating in humans: reflex effects of drinking
A. Takamata, G. W. Mack, C. M. Gillen, A. C. Jozsi and E. R. Nadel
John B. Pierce Laboratory, Yale University School of Medicine, New Haven, Connecticut 06519.
To gain better insight into the interaction between thermoregulation and
osmoregulation, we examined the thermal sweating response to drinking in
cell-dehydrated humans. Cell dehydration (CDH) was induced by infusion of a
3% NaCl solution, at 1.2 ml/kg, for 2 h; infusion of a 0.9% NaCl solution
in a separate experiment served as a control (euhydrated condition, EH).
After infusion, subjects were heated by immersion of the lower legs in 42
degrees C water at an ambient temperature of 28 degrees C for 90 min.
Subjects drank 4.3 ml/kg of H2O (approximately 38 degrees C) at 60 min of
heating. The 3% NaCl infusion increased plasma osmolality by 13.6 +/- 0.8
mosmol/kgH2O and plasma arginine vasopressin concentration ([AVP]) by 3.3
+/- 0.7 pg/ml. Neither variable was altered with 0.9% NaCl infusion. Before
drinking, esophageal temperature (Tes) had increased by 0.91 +/- 0.08
degrees C in CDH and by 0.40 +/- 0.11 degrees C in EH. Local chest sweating
rate (SRch) had increased by 0.67 +/- 0.08 and 0.63 +/- 0.07 mg.min-1.cm-2
in CDH and EH, respectively. Thus the change in SRch per unit rise in Tes
was much lower in CDH than in EH. Drinking immediately increased SRch and
reduced Tes in CDH, with a reduction in plasma [AVP] and thirst rating.
Drinking did not change thermoregulatory and osmoregulatory responses in
EH. These results suggest that the act of drinking itself eliminates, at
least partially, an osmotic inhibitory input to the thermoregulatory
center, as well as osmotic AVP secretion and thirst.
