Document Detail

Pulmonary artery smooth muscle activation attenuates arterial dysfunction during acute pulmonary hypertension.
MedLine Citation:
PMID:  15489257     Owner:  NLM     Status:  MEDLINE    
Acute pulmonary hypertension (PH) may arise with or without an increase in vascular smooth muscle (VSM) tone. Our objective was to determine how VSM activation affects both the conduit (CF) and wall buffering (BF) functions of the pulmonary artery (PA) during acute PH states. PA instantaneous flow, pressure, and diameter of six sheep were recorded during normal pressure (CTL) and different states of acute PH: 1) passively induced by PA mechanical occlusion (PPH); 2) actively induced by intravenous administration of phenylephrine (APH); and 3) a combination of both (APPH). To evaluate the direct effect of VSM activation, isobaric (PPH vs. APH) and isometric (CTL vs. APPH) analyses were performed. We calculated the local BF from the elastic (EPD) and viscous (etaPD) indexes as etaPD/EPD and the characteristic impedance (ZC) from pressure and flow to evaluate CF as 1/ZC. We also calculated the absolute and normalized cross-sectional pulsatility (PCS and NPCS, respectively), the dynamic compliance (CDYN), the cross-sectional distensibility (DCS), and the pressure-strain elastic modulus (EP). The isobaric analysis showed increase of CF, BF, and etaPD (P < 0.01) and decrease of EPD (P < 0.05) during APH in respect to PPH (concomitant with isobaric VSM activation-induced vasoconstriction, P < 0.01). The isometric analysis showed increase of E(PD) and etaPD (P < 0.01), nonsignificant difference in BF (even in the presence of a significant mean PA pressure rise, from 14 (SD 6) to 25 (SD 8) mmHg, P < 0.01), and decrease in CF (P < 0.01) during APPH respect to CTL. Mechanical occlusions (PPH and APPH) reduced BF (P < 0.01) and increased EPD (P < 0.05) with regard to their previous steady states (CTL and APH). Nonsignificant differences were found in EPD between PPH and APPH. VSM activation (APH and APPH) increased etaPD (P < 0.01) respect to their previous passive states (CTL and PPH), but no significant differences were found within similar levels of VSM activation. In conclusion, VSM plays a relevant role in main pulmonary artery function during acute pulmonary hypertension, because isobaric vasoconstriction induced by VSM activation improves both BF and CF, mainly due to the increase in etaPD concomitant with the arterial compliance. CDYN and DCS were the more pertinent clinical indexes of arterial elasticity. Additionally, the etaPD-mediated preservation of the BF could be evaluated by the geometric related indexes (PCS and NPCS), which appear to be qualitative markers of arterial wall viscosity status.
Daniel Bia Santana; Juan Gabriel Barra; Juan Carlos Grignola; Fernando Florencio Ginés; Ricardo Luis Armentano
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2004-10-15
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  98     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2005 Feb 
Date Detail:
Created Date:  2005-01-14     Completed Date:  2005-05-24     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  605-13     Citation Subset:  IM    
Departamento de Fisiología, Facultad de Medicina, Universidad de la República, General Flores 2125, PC 11800, Montevideo, Uruguay.
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MeSH Terms
Acute Disease
Blood Pressure
Computer Simulation
Hypertension, Pulmonary / diagnosis,  physiopathology*
Models, Cardiovascular*
Muscle Contraction*
Muscle, Smooth, Vascular / drug effects,  physiopathology*
Phenylephrine / administration & dosage
Pulmonary Artery / drug effects,  physiopathology*
Severity of Illness Index
Vascular Resistance
Vasoconstrictor Agents / administration & dosage
Reg. No./Substance:
0/Vasoconstrictor Agents; 59-42-7/Phenylephrine

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