Ultra-high-resolution scanning electron microscopy of the sarcoplasmic reticulum of the rat atrial myocardial cells

✍ Scribed by Yamasaki, Yuichi ;Furuya, Yasuo ;Araki, Keijiro ;Matsuura, Kimio ;Kobayashi, Michiya ;Ogata, Takuro

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 585 KB
• Volume: 248
• Category: Article
• ISSN: 0003-276X
• DOI: 10.1002/(sici)1097-0185(199705)248:1<70::aid-ar8>3.0.co;2-j

✦ Synopsis

Background:

The sarcoplasmic reticulum (sr) of mammalian ventricular and atrial muscles share common features but also differ because t-tubules are rare and extended junctional sr is exclusively seen in the atrium. this scanning electron microscope (sem) study was undertaken to clarify the three-dimensional organization of the rat atrial sr system. specific preparations were examined with an ultra-high-resolution sem.

Methods:

Fixed right rat atria were frozen, fractured, and macerated by the aldehyde-osmium-dmso-osmium method to remove myofibrils and cytoplasmic matrix. left exposed were mitochondria, sr, and sarcolemma. dried specimens were then impregnated by osmium-hydrazine and examined without metal coating.

Results:

In place of conventional t-tubules, a prominent type of sarcotubules, z-tubules, were found at the z-line level. branches from these tubules joined the cisternal sr, which was 100-300 nm in diameter and localized near the z-line, and formed extensive sr meshworks and polygonal patches. bulbous swellings, the corbular sr, were also evident. sarcotubular reticulum completely surrounded each myofibril. the intermyofibrillar sr, especially z-tubules, joined the peripheral subsarcolemmal sr, which was also arranged as a meshwork and was closely apposed to the sarcolemma.

Conclusions:

These sem observations confirm the organization of the rat atrial sr system and present new, detailed, three-dimensional images of z-tubules, cisternal sr, extended junctional sr, and peripheral sr, which provide further structural insight.