水盐负荷改变时分泌心房钠尿肽的心房特殊颗粒数目与其钙含量的相关变化

RELATIVE CHANGES BETWEEN CALCIUM CONTENT AND NUMBER OF ATRIAL SPECIFIC GRANULES INDUCED BY WATER AND SALT LOADING

本文报道大鼠水盐负荷时，其心房特殊颗粒（ＡＳＧ）的数目及钙含量发生相关变化。给大鼠禁水５ｄ或饮２％ＮａＣｌ液４ｄ造成水盐负荷，用电镜形态计量法计数ＡＳＧ，以反映心房钠尿肽（ＡＮＰ）的分泌水平，电镜Ｘ射线显微分析法测定ＡＳＧ中钙、硫含量及肌质同终末池（ＴＳＲ）中钙含量。结果显示，禁水引起ＡＮＰ分泌减少时，ＡＳＧ的数密度增加（６．０２±２．３０增至９．９７±３．２１个／μｍ３），同时伴有钙含量增加（６４±１６增至９２±１８ｍｍｏｌ／ｋｇ）；饮盐水引起ＡＮＰ分泌增加时，ＡＳＧ的数密度减少（６．０２±２．３０减至２．９６±１．６２个／μｍ３），巨伴有钙含量减少（６４±１６减至３８±２２ｍｍｏｌ／ｋｇ），但水盐负荷对ＴＳＲ中钙浓度无任何影响。据此推论ＡＳＧ作为细胞内钙库，借某种机制调控其中钙的释放而参与ＡＮＰ的刺激分泌耦联过程。

Rats prepared by either deprivation of water intake for 5 d or drinking 2% NaCl solution for 4 d were sacrificed for dissection of auricle, and making ultrathin sections.The numerical density (Nv) of atrial specific granules (ASG) were counted by using electron microscopic morphometry, and Ca concentration in ASG and in terminal cisterna of sarcoplasmic reticulum (TSR) was determined by using electron microscopic Xray microanalysis. In the drinking 2% NaCl solution group, the Nv of ASG decreased from 6. 02±2. 30 to 2. 96±1. 62/μm3 (P<0. 01 ) and all companied by a decrease of Ca concentration from 64±16 to 38±21 mmol/kg (P<0. 01), while the secretion of atrial natriuretic peptide (ANP) showed some increase. Water deprivation induced all the contrary results. However, the Ca concentration in TSR was not affected by weter-salt loading. It is suggested that when the atrial cardiocytes were stimulated by salt loading, Ca in ASG was released into cytosol and thus promoted fusion of ASG membrane with sarcolemma which resulted in release of ANP. Therefore, it is considered that ASG as an intracellular Ca store participates in the stimulus-secretion coupling of ANP through the release of Ca ions.