Affiliation:
1. From the Department of Physiology, University of Auckland, Auckland, NZ.
Abstract
Abstract
—The transverse tubular system (t-system) of cardiac muscle is a structure that allows rapid propagation of excitation into the cell interior. Using 2-photon molecular excitation microscopy and digital image–processing methods, we have obtained a comprehensive overview of the t-system of rat ventricular myocytes in living cells. We show that it is possible to quantify the morphology of the t-system in terms of average local tubule diameter, branching pattern, and local abundance of the t-system by immersing living myocytes in a dextran-linked fluorescein solution. Our data suggest that previous electron microscopic examinations of t-system structure have underestimated both the geometric complexity of the t-system morphology and the fraction of cell volume occupied by the t-system (3.6% in this species). About 40% of tubules occur between Z-lines, and the t-tubule diameter is 255±0.85 nm (mean±SEM). The t-tubules leave the outer surface of the cell in an approximately rectangular array; however, at some points junctions between the t-tubules and the surface membrane are missing. In view of the complexity of the t-system apparent from our images, we propose that the t-system be renamed the “sarcolemmal Z rete.” The methods presented here are generally applicable to the quantification of the sarcolemmal Z rete and other structures within cells by fluorescence microscopy in a variety of cell types.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine,Physiology
Reference41 articles.
1. Sommer JR Johnson EA. Ultrastructure of cardiac muscle. In: Berne RM Sperelakis N Geiger SR eds. Handbook of Physiology: The Cardiovascular System . Vol. 1 Section 2. Bethesda Md: American Physiological Society; 1979:113–186.
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