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首页> 外文期刊>American Journal of Physiology >Hypoxic acclimation negatively impacts the contractility of steelhead trout (Oncorhynchus mykiss) spongy myocardium
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Hypoxic acclimation negatively impacts the contractility of steelhead trout (Oncorhynchus mykiss) spongy myocardium

机译：缺氧驯化产生负面影响Steelhead Trout（Oncorhynchus mykiss）海绵状心肌的收缩性

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摘要

Cardiac stroke volume (SV) is compromised in Atlantic cod and rainbow trout following acclimation to hypoxia (i.e., 40% air saturation; ~8 kPa O2) at 10-12°C, and this is not due to changes in heart morphometrics or maximum achievable in vitro end-diastolic volume. To examine if this diminished SV may be related to compromised myocardial contractility, we used the work-loop method to measure work and power in spongy myocardial strips from normoxic- and hypoxic-acclimated steelhead trout when exposed to decreasing Po2 levels (21 to 1.5 kPa) at several frequencies (30-90 contractions/min) at 14°C (their acclimation temperature). Work required to lengthen the muscle, as during filling of the heart, was strongly frequency dependent (i.e., increased with contraction rate) but was not affected by hypoxic acclimation or test Po2. In contrast, although shortening work was less frequency dependent, this parameter and network (and power) 1) were consistently lower (by ~30-50 and ~15%, respectively) in strips from hypoxic-acclimated fish and 2) fell by ~40-50% in both groups from 20 to 1.5 kPa Po2, despite the already-reduced myocardial performance in the hypoxic-acclimated group. In addition, strips from hypoxic-acclimated trout showed a poorer recovery of net power (by ~15%) when returned to normoxia. These results strongly suggest that hypoxic acclimation reduces myocardial contractility, and in turn, may limit SV (possibly by increasing end-systolic volume), but that this diminished performance does not improve the capacity to maintain myocardial performance under oxygen limiting conditions.
机译：在10-12°C时适应缺氧（即40％的空气饱和度;〜8kPa O2），在大西洋鳕鱼和虹鳟鱼中遭到大西洋鳕鱼和虹鳟鱼，并且这不是由于心脏形态量学或最大变化可实现的体外端舒张分体积。为了检查这种减少的SV可能与受损的心肌收缩性有关，我们使用工作循环方法在暴露于降低PO2水平（21至1.5kPa ）在14°C（适应温度）的几个频率（30-90收缩/分钟）上。延长肌肉所需的工作是在填充心脏期间的强烈依赖性（即，由于收缩率增加），但不受缺氧适应或试验PO2的影响。相反，虽然缩短工作较少频率依赖性较少，但该参数和网络（和电源）1）始终如一（分别〜30-50〜15％，分别）从缺氧适应的鱼类和2）下降〜尽管缺氧适应群体中已经降低了40-1.5kPa PO2，但两组两组中的40-50％。此外，来自缺氧 - 适应的鳟鱼的条带表现出净功率的较差，当返回到常氧时，净功率恢复较差（〜15％）。这些结果强烈表明，缺氧驯化减少了心肌收缩性，然后可能会限制SV（可能通过增加终端 - 收缩量），但这种减少的性能不会提高在氧气限制条件下保持心肌性能的能力。

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