Seccia T M, Atlante A, Vulpis V, Marra E, Passarella S, Pirrelli A
Cattedra di Medicina Interna, CNR, Università degli Studi, Bari.
Cardiologia. 1999 Aug;44(8):719-25.
The aim of this study was to investigate the kinetic properties of inorganic phosphate (Pi) translocator in intact mitochondria isolated from the hypertrophied left ventricular tissue of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) at the ages of 5 and 24 weeks, before and after the development of hypertension.
The dependence of the Pi uptake rate on substrate concentration was measured in both absence and presence of mersalyl by spectroscopic techniques.
Saturation characteristics were found (Km 250.0 +/- 25.0 and 15.0 +/- 1.5 microM for 5- and 24-week-old SHR, and 300.0 +/- 30.0 and 40.0 +/- 4.5 microM for WKY rat mitochondria, respectively, p < 0.05; Vmax 1.2 +/- 0.16 and 0.1 +/- 0.01 delta A/min x mg mitochondrial proteins for 5- and 24-week-old SHR, and 4.1 +/- 0.39 and 1.4 +/- 0.12 delta A/min x mg mitochondrial proteins for 5- and 24-week-old WKY rats, respectively, p < 0.05). When Pi carrier activity was measured using concentrations which are assumed to be in the cytosol under physiological conditions, Pi carrier velocity was 1.1 and 0.1 in SHR and 4.6 and 1.4 delta A/min x mg mitochondrial proteins in WKY, at 5 and 24 weeks, respectively.
The significant decrease in the activity of the Pi carrier could imply that pressure overload is critical in SHR. Nevertheless, as decreased activity was found in SHR also at an early age when animals do not show stable increased blood pressure levels, we suggest that other factors might contribute to the abnormalities of Pi transport in mitochondria. An altered gene expression possibly related to a primary defect in this strain or, alternatively, to an abnormal regulation of protein synthesis might be proposed as additional factors affecting Pi carrier activity. The results of this study, together with previous data of the literature showing abnormalities in energy production mechanisms, allow us to hypothesize a profound rearrangement of energy metabolism at the mitochondrial level in this model of left ventricular hypertrophy and hypertension.
本研究旨在调查从5周龄和24周龄自发性高血压大鼠（SHR）及Wistar-Kyoto大鼠（WKY）肥厚的左心室组织中分离出的完整线粒体中无机磷酸盐（Pi）转运体的动力学特性，这些大鼠处于高血压发生之前和之后。
通过光谱技术在有无汞撒利的情况下测量Pi摄取速率对底物浓度的依赖性。
发现了饱和特性（5周龄和24周龄SHR的Km分别为250.0±25.0和15.0±1.5微摩尔，WKY大鼠线粒体的Km分别为300.0±30.0和40.0±4.5微摩尔，p<0.05；5周龄和24周龄SHR的Vmax分别为1.2±0.16和0.1±0.01ΔA/分钟×毫克线粒体蛋白，5周龄和24周龄WKY大鼠的Vmax分别为4.1±0.39和1.4±0.12ΔA/分钟×毫克线粒体蛋白，p<0.05）。当使用假定在生理条件下存在于细胞质中的浓度测量Pi载体活性时，SHR在5周龄和24周龄时Pi载体速度分别为1.1和0.1，WKY大鼠在5周龄和24周龄时分别为4.6和1.4ΔA/分钟×毫克线粒体蛋白。
Pi载体活性的显著降低可能意味着压力超负荷在SHR中至关重要。然而，由于在SHR动物未表现出稳定的血压升高水平的早期也发现活性降低，我们认为其他因素可能导致线粒体中Pi转运异常。可能与该品系的原发性缺陷相关或与蛋白质合成的异常调节相关的基因表达改变可能是影响Pi载体活性的其他因素。本研究结果与文献中先前显示能量产生机制异常的数据一起，使我们能够假设在这种左心室肥厚和高血压模型中线粒体水平的能量代谢发生了深刻的重排。
