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.
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.
Authors: Malcolm M Kirk; Leighton T Izu; Ye Chen-Izu; Stacey L McCulle; W Gil Wier; C William Balke; Stephen R Shorofsky Journal: J Physiol Date: 2003-01-31 Impact factor: 5.182
Authors: Andreas Goette; Jonathan M Kalman; Luis Aguinaga; Joseph Akar; Jose Angel Cabrera; Shih Ann Chen; Sumeet S Chugh; Domenico Corradi; Andre D'Avila; Dobromir Dobrev; Guilherme Fenelon; Mario Gonzalez; Stephane N Hatem; Robert Helm; Gerhard Hindricks; Siew Yen Ho; Brian Hoit; Jose Jalife; Young-Hoon Kim; Gregory Y H Lip; Chang-Sheng Ma; Gregory M Marcus; Katherine Murray; Akihiko Nogami; Prashanthan Sanders; William Uribe; David R Van Wagoner; Stanley Nattel Journal: Heart Rhythm Date: 2016-06-10 Impact factor: 6.343
Authors: Eckard Picht; Aleksey V Zima; Thomas R Shannon; Alexis M Duncan; Lothar A Blatter; Donald M Bers Journal: Circ Res Date: 2011-02-10 Impact factor: 17.367