著者

Tsuji Tsuyoshi Ohga Yoshimi Yoshikawa Yoshiro SAKATA Susumu KOHZUKI Hisaharu MISAWA Hiromi ABE Takehisa TABAYASHI Nobuoki KOBAYASHI Shuichi KITAMURA Soichiro TANIGUCHI Shigeki SUGA Hiroyuki TAKAKI Miyako

出版者

一般社団法人 日本生理学会

雑誌

The Japanese journal of physiology (ISSN:0021521X)

巻号頁・発行日

vol.49, no.6, pp.513-520, 1999-12-01

参考文献数

20

被引用文献数

7 23

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We have already reported the linear oxygen consumption per beat (Vo₂)&ndash;systolic pressure-volume area (PVA) relation from the curved left ventricular (LV) end-systolic pressure&ndash;volume relation (ESPVR) in the cross-circulated rat heart. The Vo₂ intercept (PVA-independent Vo₂) is primarily composed of Vo₂ for Ca²⁺ handling in excitation-contraction (E-C) coupling and basal metabolism. The aim of the present study was to obtain the oxygen cost of LV contractility that indicates Vo₂ for Ca²⁺ handling in E-C coupling per unit LV contractility change in the rat heart. Oxygen cost of LV contractility is obtainable as a slope of a linear relation between PVA-independent Vo₂ and LV contractility. We obtained a composite Vo₂&ndash;PVA relation line at a mid-range LV volume (mLVV) under gradually enhanced LV contractility by stepwise increased Ca²⁺ infusion and thus the gradually increased PVA-independent Vo₂ values. As a LV contractility index, we could not use E_max (ESP-V ratio; ESP/ESV) for the linear ESPVR because of the curved ESPVR in the rat LV. A PVA at a mLVV (PVA_mLVV) has been proposed as a good index for assessing rat LV mechanoenergetics. Since the experimentally obtained PVA_mLVV was not triangular due to the curved ESPVR, we propose an equivalent ESP-V ratio at a mLVV, (eESP/ESV)_mLVV, as a LV contractility index. This index was calculated as an ESP-V ratio of the specific virtual triangular PVA_mLVV that is energetically equivalent to the real PVA_mLVV. The present approach enabled us to obtain a linear relation between PVA-independent Vo₂ and (eESP/ESV)_mLVV and the oxygen cost of LV contractility as the slope of this relation.<br>