Meyer R, Stockem W, Schmitz M, Haas H G
Z Naturforsch C Biosci. 1982 May-Jun;37(5-6):489-501. doi: 10.1515/znc-1982-5-622.
In the present investigation different finestructural and histochemical procedures were employed to demonstrate normal morphology and Ca2+-transport mechanism in bullfrog atrial myocardium. For normal morphology specimens were fixed in 1% OsO4, 2.5% glutaraldehyde or liquid propane at -185 degrees C before they were prepared for conventional embedding and freeze-etching, respectively. Special interest was focussed on the caveolae system, which is composed of single, spherical membrane invaginations (diameter, 85 nm), randomly distributed at the entire cell periphery. The caveolae enlarge the cell surface by 24.5% and occupy 8.5% of the cellular volume. The caveolae membrane contains a few intramembraneous particles with a diameter of 8.4 nm comparable to the size of ATPases as found in other cells. For histochemistry the specimens were first stabilized by treatment with 50% glycerol, 0.025% glutaraldehyde or 0.15% formaldehyde and then incubated in a medium containing 4 mM CaCl2, 4 mM EGTA, 5 mM MgCl2, 5 mM K2C2O4, 5 mM ATP and 20 mM histidine at pH 7.0. This incubation always succeeded in the formation of electron-dense deposits with elliptical shape, measuring 100-200 nm in length and 10-30 nm in diameter. According to X-ray spectra they deliver a characteristic calcium-peak and can be found within two different cellular compartments: in small invaginations of the sarcolemma, i.e. the caveolae-system, and in the intrafibrillar sarcoplasmic reticulum. The elliptical deposits can be clearly distinguished from round electron-dense granules measuring 16 nm in diameter, which are located within randomly distributed small vesicles and composed of potassium and phosphate. Contrary to the elliptical deposits the round granules are also present in controls and seem to be identical with the so-called atrial granules. In comparison to observations obtained with the same method in other muscular systems and derived from various control experiments the results of this study favour the existence of an ATP-dependent Ca2+-pumping mechanism in frog atrial muscle bound to both, the sarcoplasmic reticulum and the caveolae system.
在本研究中，采用了不同的超微结构和组织化学方法来展示牛蛙心房肌的正常形态和Ca2+转运机制。为观察正常形态，分别在常规包埋和冷冻蚀刻前，将标本固定于1%四氧化锇、2.5%戊二醛或-185℃的液态丙烷中。特别关注的是小窝系统，它由单个球形膜内陷（直径85nm）组成，随机分布于整个细胞周边。小窝使细胞表面积增大24.5%，占细胞体积的8.5%。小窝膜含有一些直径为8.4nm的膜内颗粒，其大小与其他细胞中发现的ATP酶相当。对于组织化学，标本先用50%甘油、0.025%戊二醛或0.15%甲醛处理以稳定，然后在含有4mM氯化钙、4mM乙二醇双四乙酸、5mM氯化镁、5mM草酸钾、5mM三磷酸腺苷和20mM组氨酸（pH7.0）的培养基中孵育。这种孵育总能成功形成椭圆形的电子致密沉积物，长度为100 - 200nm，直径为10 - 30nm。根据X射线光谱，它们呈现出特征性的钙峰，可在两个不同的细胞区室中发现：肌膜的小内陷处，即小窝系统，以及肌原纤维内的肌浆网中。椭圆形沉积物可与直径为16nm的圆形电子致密颗粒明显区分，后者位于随机分布的小泡内，由钾和磷酸盐组成。与椭圆形沉积物不同，圆形颗粒在对照中也存在，似乎与所谓的心房颗粒相同。与用相同方法在其他肌肉系统中获得的观察结果以及各种对照实验相比，本研究结果支持在蛙心房肌中存在一种与肌浆网和小窝系统均相关的依赖三磷酸腺苷的Ca2+泵机制。
