HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 98/2/605    most recent 00361.2004v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Santana, D. B. Articles by Armentano, R. L. Search for Related Content PubMed PubMed Citation Articles by Santana, D. B. Articles by Armentano, R. L.

Pulmonary artery smooth muscle activation attenuates arterial dysfunction during acute pulmonary hypertension

¹Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay; ²Facultad de Ingeniería, y Ciencias Exactas y Naturales, Universidad Favaloro, Buenos Aires, Argentina

Submitted 12 April 2004 ; accepted in final form 8 October 2004

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 (E_PD) and viscous (_PD) indexes as _PD/E_PD and the characteristic impedance (Z_C) from pressure and flow to evaluate CF as 1/Z_C. We also calculated the absolute and normalized cross-sectional pulsatility (P_CS and NP_CS, respectively), the dynamic compliance (C_DYN), the cross-sectional distensibility (D_CS), and the pressure-strain elastic modulus (E_P). The isobaric analysis showed increase of CF, BF, and _PD (P < 0.01) and decrease of E_PD (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 _PD (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 E_PD (P < 0.05) with regard to their previous steady states (CTL and APH). Nonsignificant differences were found in E_PD between PPH and APPH. VSM activation (APH and APPH) increased _PD (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 _PD concomitant with the arterial compliance. C_DYN and D_CS were the more pertinent clinical indexes of arterial elasticity. Additionally, the _PD-mediated preservation of the BF could be evaluated by the geometric related indexes (P_CS and NP_CS), which appear to be qualitative markers of arterial wall viscosity status.

buffering function; arterial wall viscoelasticity; characteristic impedance

This article has been cited by other articles:

				H. Syyong, C. Cheung, D. Solomon, C. Y. Seow, and K. H. Kuo Adaptive response of pulmonary arterial smooth muscle to length change J Appl Physiol, April 1, 2008; 104(4): 1014 - 1020. [Abstract] [Full Text] [PDF]

				R. L. Armentano, J. G. Barra, D. B. Santana, F. M. Pessana, S. Graf, D. Craiem, L. M. Brandani, H. P. Baglivo, and R. A. Sanchez Smart Damping Modulation of Carotid Wall Energetics in Human Hypertension: Effects of Angiotensin-Converting Enzyme Inhibition Hypertension, March 1, 2006; 47(3): 384 - 390. [Abstract] [Full Text] [PDF]