Document Detail

Influence of plasma osmolality on baroreflex control of sympathetic activity.
MedLine Citation:
PMID:  17644564     Owner:  NLM     Status:  MEDLINE    
The purpose of this study was to determine if plasma osmolality alters baroreflex control of sympathetic activity when controlling for a change in intravascular volume; we hypothesized that baroreflex control of sympathetic activity would be greater during a hyperosmotic stimulus compared with an isoosmotic stimulus when intravascular volume expansion was matched. Seven healthy subjects (25 +/- 2 yr) completed two intravenous infusions: a hypertonic saline infusion (HSI; 3% NaCl) and, on a separate occasion, an isotonic saline infusion (ISO; 0.9% NaCl), both at a rate of 0.15 ml x kg(-1) x min(-1). To isolate the effect of osmolality, comparisons between HSI and ISO conditions were retrospectively matched based on hematocrit; therefore, baroreflex control of sympathetic outflow was determined at 20 min of a HSI and 40 min of an ISO. Muscle sympathetic outflow (MSNA) was directly measured using the technique of peroneal microneurography; osmolality and blood pressure (Finometer) were assessed. The baroreflex control of sympathetic outflow was estimated by calculating the slope of the relationship between MSNA and diastolic blood pressure during controlled breathing. Plasma osmolality was greater during the HSI compared with the ISO (HSI: 292 +/- 0.9 mosmol/kg and ISO: 289 +/- 0.8 mosmol/kg, P < 0.05). Hematocrits were matched (HSI: 39.1 +/- 1% and ISO: 39.1 +/- 1%, P > 0.40); thus, we were successful in isolating osmolality. The baroreflex control of sympathetic outflow was greater during the HSI compared with the ISO (HSI: -8.3 +/- 1.2 arbitrary units x beat(-1) x mmHg(-1) vs. ISO: -4.0 +/- 0.8 arbitrary units x beat(-1) x mmHg(-1), P = 0.01). In conclusion, when controlling for intravascular volume, increased plasma osmolality enhances baroreflex control of sympathetic activity in humans.
Megan M Wenner; William C Rose; Erin P Delaney; Michael E Stillabower; William B Farquhar
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, N.I.H., Extramural     Date:  2007-07-20
Journal Detail:
Title:  American journal of physiology. Heart and circulatory physiology     Volume:  293     ISSN:  0363-6135     ISO Abbreviation:  Am. J. Physiol. Heart Circ. Physiol.     Publication Date:  2007 Oct 
Date Detail:
Created Date:  2007-10-09     Completed Date:  2007-11-21     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100901228     Medline TA:  Am J Physiol Heart Circ Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  H2313-9     Citation Subset:  IM    
Department of Health, Nutrition, College of Health Sciences, University of Delaware, Delaware 19716, USA.
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MeSH Terms
Blood Pressure
Blood Volume*
Chlorides / blood
Heart Rate
Infusions, Intravenous
Isotonic Solutions
Muscle, Skeletal / innervation*
Osmolar Concentration
Potassium / blood
Retrospective Studies
Saline Solution, Hypertonic / administration & dosage*,  chemistry
Sodium / blood
Sodium Chloride / administration & dosage*,  chemistry
Sympathetic Nervous System / physiology*
Time Factors
Grant Support
1-R15-HL-074851-01/HL/NHLBI NIH HHS
Reg. No./Substance:
0/Chlorides; 0/Isotonic Solutions; 0/Saline Solution, Hypertonic; 7440-09-7/Potassium; 7440-23-5/Sodium; 7647-14-5/Sodium Chloride

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