Document Detail


Venous tone in the developmental stages of spontaneous hypertension.
MedLine Citation:
PMID:  9449405     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The initial stages of hypertension in the spontaneously hypertensive rat (SHR) are characterized by an increase in cardiac output. Venous capacitance plays an important role in the control of cardiac output. This study tested the hypothesis that venous tone is elevated in the developmental stages of spontaneous hypertension. Male SHR or normotensive Wistar-Kyoto (WKY) rats were instrumented for the measurement of arterial pressure (FAP) and intrathoracic vena caval pressure (FVP). A latex-tipped catheter was advanced into the right atrium via the jugular vein. Mean circulatory filling pressure (MCFP), an index of integrated venomotor tone, was calculated as MCFP=FVP+(FAP-FVP)/VAR. FAP and FVP were recorded after 5 seconds of right atrial balloon inflation. The venous to arterial compliance ratio (VAR) was estimated as 76 for WKY and 106 for SHR. Mean arterial pressure (MAP), heart rate, and MCFP were recorded in conscious rats of 4 to 6 and 8 to 10 weeks of age. In 4- to 6-week-old rats, both MAP and MCFP were significantly elevated in the SHR (MAP, 129+/-6 mm Hg; MCFP, 6.6+/-0.4 mm Hg) compared with the age-matched WKY (MAP, 91+/-6 mm Hg; MCFP, 5.4+/-0.4 mm Hg), whereas heart rate was not significantly different. The elevations in MAP (SHR, 144+/-4 mm Hg; WKY, 102+/-3 mm Hg) and MCFP (SHR, 7.7+/-0.3 mm Hg; WKY, 6.0+/-0.2 mm Hg) in SHR were exaggerated at 8 to 10 weeks of age. After ganglionic blockade (chlorisondamine; 10 mg/kg), the differences in MCFP were no longer statistically significant between SHR and WKY at both 4 to 6 weeks of age (3.9+/-0.2 versus 4.0+/-0.3 mm Hg) and 8 to 10 weeks of age (5.0+/-0.3 versus 4.3+/-0.3 mm Hg, respectively). The differences in MAP at 4 to 6 weeks of age (79+/-7 versus 67+/-5 mm Hg, respectively) also were not statistically significant after ganglionic blockade. However, a significant difference in MAP between strains remained after ganglionic blockade in 8- to 10-week-old rats (90+/-5 versus 63+/-3 mm Hg, respectively). These findings indicate that venous tone is increased via autonomic effector systems during the developmental stages of spontaneous hypertension. These data also suggest that autonomic mechanisms predominate at very early stages, whereas nonautonomic mechanisms assume more importance in maintaining the elevated MAP as hypertension progresses.
Authors:
D S Martin; M C Rodrigo; C W Appelt
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Hypertension     Volume:  31     ISSN:  0194-911X     ISO Abbreviation:  Hypertension     Publication Date:  1998 Jan 
Date Detail:
Created Date:  1998-02-03     Completed Date:  1998-02-03     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  7906255     Medline TA:  Hypertension     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  139-44     Citation Subset:  IM    
Affiliation:
Department of Physiology and Pharmacology, University of South Dakota School of Medicine, Vermillion 57069-2390, USA. dsmartin@sunflowr.usd.edu
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MeSH Terms
Descriptor/Qualifier:
Animals
Autonomic Nervous System / drug effects,  physiopathology
Blood Pressure* / drug effects
Chlorisondamine / pharmacology
Ganglionic Blockers / pharmacology
Heart Rate / drug effects
Hypertension / physiopathology*
Male
Rats
Rats, Inbred SHR
Rats, Inbred WKY
Veins / physiology,  physiopathology*
Venous Pressure
Grant Support
ID/Acronym/Agency:
47407//PHS HHS
Chemical
Reg. No./Substance:
0/Ganglionic Blockers; 7701-62-4/Chlorisondamine

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