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. 2005 Feb 14;102(8):3099–3104. doi: 10.1073/pnas.0500059102

Fig. 1.

Fig. 1.

Microanatomy of SR in rabbit cardiac cells. (A) Longitudinal section of rabbit left ventricular myocyte, showing junctional SR (jSR) cisternae near T tubules (T) and free SR (fSR). Arrowheads indicate continuities between jSR and fSR. (B and C) Details from A. Connections between jSR and fSR (arrowheads in B) were seen in 60 of 136 cisterna profiles in 60-nm-thick sections only at the periphery of the flat jSR cisternae. The average number of connections was therefore estimated to be 4.3 for a 592-nm-diameter jSR cisterna. (D) Tangential view of fSR network: Cross section at the level of the Z line. jSR cisternae (bracketed by arrowheads) are apposed either to T tubules (T) or the surface membrane. Profiles of fSR are seen next to a mitochondrion. (E) The cytoplasmic domains of ryanodine receptors (RyRs) are seen as feet in the gap between jSR and T tubule membranes (between arrows). (F) Diagram showing the relationship between the fSR network, the flat jSR cisternae, T tubules, and feet in rabbit ventricle.