Document Detail

Plasma hyperosmolality augments peripheral vascular response to baroreceptor unloading during heat stress.
MedLine Citation:
PMID:  15845884     Owner:  NLM     Status:  MEDLINE    
The aim of this study was to elucidate the interactive effect of central hypovolemia and plasma hyperosmolality on regulation of peripheral vascular response and AVP secretion during heat stress. Seven male subjects were infused with either isotonic (0.9%; NOSM) or hypertonic (3.0%; HOSM) NaCl solution and then heated by perfusing 42 degrees C (heat stress; HT) or 34.5 degrees C water (normothermia; NT) through water perfusion suits. Sixty minutes later, subjects were exposed to progressive lower body negative pressure (LBNP) to -40 mmHg. Plasma osmolality (P(osmol)) increased by approximately 11 mosmol/kgH(2)O in HOSM conditions. The increase in esophageal temperature before LBNP was much larger in HT-HOSM (0.90 +/- 0.09 degrees C) than in HT-NOSM (0.30 +/- 0.07 degrees C) (P < 0.01) because of osmotic inhibition of thermoregulation. During LBNP, mean arterial pressure was well maintained, and changes in thoracic impedance and stroke volume were similar in all conditions. Forearm vascular conductance (FVC) before application of LBNP was higher in HT than in NT conditions (P < 0.001) and was not influenced by P(osmol) within the thermal conditions. The reduction in FVC at -40 mmHg in HT-HOSM (-9.99 +/- 0.96 units; 58.8 +/- 4.1%) was significantly larger than in HT-NOSM (-6.02 +/- 1.23 units; 44.7 +/- 8.1%) (P < 0.05), whereas the FVC response was not different between NT-NOSM and NT-HOSM. Plasma AVP response to LBNP did not interact with P(osmol) in either NT or HT conditions. These data indicate that there apparently exists an interactive effect of P(osmol) and central hypovolemia on the peripheral vascular response during heat stress, or peripheral vasodilated conditions, but not in normothermia.
Tomoyuki Ito; Toshiyuki Itoh; Takashi Hayano; Katsuya Yamauchi; Akira Takamata
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2005-04-21
Journal Detail:
Title:  American journal of physiology. Regulatory, integrative and comparative physiology     Volume:  289     ISSN:  0363-6119     ISO Abbreviation:  Am. J. Physiol. Regul. Integr. Comp. Physiol.     Publication Date:  2005 Aug 
Date Detail:
Created Date:  2005-07-14     Completed Date:  2005-09-01     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  100901230     Medline TA:  Am J Physiol Regul Integr Comp Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  R432-R440     Citation Subset:  IM    
Department of Physiology, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto, Japan.
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MeSH Terms
Arginine Vasopressin / blood
Blood / metabolism*
Blood Vessels / physiopathology
Forearm / blood supply*
Heat Stress Disorders / physiopathology*
Hormones / blood
Hypovolemia / physiopathology
Lower Body Negative Pressure
Osmolar Concentration
Pressoreceptors / physiopathology*
Saline Solution, Hypertonic / pharmacology
Reg. No./Substance:
0/Hormones; 0/Saline Solution, Hypertonic; 113-79-1/Arginine Vasopressin

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