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

We have already reported the linear oxygen consumption per beat (Vo<sub>2</sub>)&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 Vo<sub>2</sub> intercept (PVA-independent Vo<sub>2</sub>) is primarily composed of Vo<sub>2</sub> for Ca<sup>2+</sup> 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 Vo<sub>2</sub> for Ca<sup>2+</sup> 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 Vo<sub>2</sub> and LV contractility. We obtained a composite Vo<sub>2</sub>&ndash;PVA relation line at a mid-range LV volume (mLVV) under gradually enhanced LV contractility by stepwise increased Ca<sup>2+</sup> infusion and thus the gradually increased PVA-independent Vo<sub>2</sub> values. As a LV contractility index, we could not use E<sub>max</sub> (ESP-V ratio; ESP/ESV) for the linear ESPVR because of the curved ESPVR in the rat LV. A PVA at a mLVV (PVA<sub>mLVV</sub>) has been proposed as a good index for assessing rat LV mechanoenergetics. Since the experimentally obtained PVA<sub>mLVV</sub> was not triangular due to the curved ESPVR, we propose an equivalent ESP-V ratio at a mLVV, (eESP/ESV)<sub>mLVV</sub>, as a LV contractility index. This index was calculated as an ESP-V ratio of the specific virtual triangular PVA<sub>mLVV</sub> that is energetically equivalent to the real PVA<sub>mLVV</sub>. The present approach enabled us to obtain a linear relation between PVA-independent Vo<sub>2</sub> and (eESP/ESV)<sub>mLVV</sub> and the oxygen cost of LV contractility as the slope of this relation.<br>