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

This Article Full Text Full Text (PDF) All Versions of this Article: 297/5/H1736    most recent 00672.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Nakajima-Takenaka, C. Articles by Takaki, M. PubMed PubMed Citation Articles by Nakajima-Takenaka, C. Articles by Takaki, M.

Left ventricular function of isoproterenol-induced hypertrophied rat hearts perfused with blood: mechanical work and energetics

¹Department of Physiology II, Nara Medical University, 840 Shijo-cho, Kashihara, Nara; and ²Life Sciences Research Center, ³Hypertension and Kidney Research Center and ⁴Department of Pharmacology, Kagawa University Medical School, Kagawa, Japan

Submitted July 17, 2009 ; accepted in final form September 1, 2009

We investigated left ventricular (LV) mechanical work and energetics in the cross-circulated (blood-perfused) isoproterenol [Iso 1.2 mg·kg^–1·day^–1 for 3 days (Iso3) or 7 days (Iso7)]-induced hypertrophied rat heart preparation under isovolumic contraction-relaxation. We evaluated pressure-time curves per beat, end-systolic pressure-volume and end-diastolic pressure-volume relations, and myocardial O₂ consumption per beat (O₂)-systolic pressure-volume area (PVA; a total mechanical energy per beat) linear relations at 240 beats/min, because Iso-induced hypertrophied hearts failed to completely relax at 300 beats/min. The LV relaxation rate at 240 beats/min in Iso-induced hypertrophied hearts was significantly slower than that in control hearts [saline 24 µl/day for 3 and 7 days (Sa)] with unchanged contraction rate. The O₂-intercepts (composed of basal metabolism and Ca²⁺ cycling energy consumption in excitation-contraction coupling) of O₂-PVA linear relations were unchanged associated with their unchanged slopes in Sa, Iso3, and Iso7 groups. The oxygen costs of LV contractility were also unchanged in all three groups. The amounts of expression of sarcoplasmic reticulum Ca²⁺-ATPase, phospholamban (PLB), phosphorylated-Ser¹⁶ PLB, phospholemman, and Na⁺-K⁺-ATPase are significantly decreased in Iso3 and Iso7 groups, although the amount of expression of NCX1 is unchanged in all three groups. Furthermore, the marked collagen production (types I and III) was observed in Iso3 and Iso7 groups. These results suggested the possibility that lowering the heart rate was beneficial to improve mechanical work and energetics in isoproterenol-induced hypertrophied rat hearts, although LV relaxation rate was slower than in normal hearts.

cardiac function; excitation-contraction coupling; systolic pressure-volume area; oxygen consumption