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研究心房钠尿肽分泌过程是否与心房特殊颗粒中钙的释放有关，需首先阐明心房特殊颗粒是否含有高浓度钙。本工作用电镜Ｘ射线显微分析技术定量地测定心房特殊颗粒中钙的浓度。新鲜大鼠心房经快速冷冻后作冷冻超薄切片，在ＪＥＭ－１２００ＥＸ分析电镜（附有ＬｉｎｋＡＮ１００００能量分散型Ｘ射线分光仪）下进行测定。１０次测定结果显示心房特殊颗粒含较高浓度的钙，平均值达８１±１５ｍｍｏｌ／ｋｇ，接近肌质网中钙的浓度。用Ｃａ２＋－ＡＴＰ酶电镜细胞化学技术证实酶反应产物存在于心房特殊颗粒的包膜上。推想颗粒包膜上的Ｃａ２＋－ＡＴＰ酶能将钙从胞质溶胶中推向颗粒内，并维持颗粒内的高钙浓度。因此认为心房特殊颗粒是心房肌细胞中的又一种细胞内钙库。
To investigate whether the atrial natriuretic peptide secretion process is related to the release of calcium from specific atrial particles, it is necessary to first elucidate whether atrial specific particles contain high concentrations of calcium. This work using electron microscopy X-ray microanalysis quantitative determination of calcium in atrial specific particle concentration. Frozen ultrathin sections of fresh rat atria were frozen quickly and assayed on a JEM-1200EX analytical electron microscope (with a LinkAN 10000 energy dispersive X-ray spectrometer). The results of 10 measurements showed that the atrium specific particles contained a higher concentration of calcium with an average of 81 ± 15 mmol / kg, which was close to the concentration of calcium in the sarcoplasmic reticulum. Electron microscopy cytochemistry with Ca2 + -ATP enzyme confirmed that the enzyme reaction product was present on the envelope of the atrial specific granules. It is hypothesized that the Ca2 + -ATPase on the granular envelope will push calcium from the cytosol into the particle and maintain a high calcium concentration within the particle. So that atrial special particles is another intracellular calcium in atrial myocytes.