ISSN:
1432-0878
Keywords:
Mammalian cardiac muscle
;
T system
;
Longitudinal tubules
;
Electronopaque diffusion tracers
;
Excitation-contraction coupling
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Colloidal ThO2 particles (diameter of ∼ 60 Å) were used as electron-opaque markers to trace the “intracellular” compartments continuous with the bulk interstitial fluid of guinea pig ventricular muscle. Beating and quiescent hearts in a Langendorff preparation were perfused for 30 min with oxygenated Ringer solution containing 1% ThO2. The hearts were immediately fixed by perfusing with glutaraldehyde solution. The colloidal ThO2 particles entered into many of the T tubules and into longitudinallyrunning tubules. No differences in distribution of ThO2 were observed in a heart which was not exposed to ThO2 until after it was fixed. Tracer did not penetrate into the intercalated disk clefts in the guinea pig hearts and one frog heart used for comparison. Tubular profiles filled with ThO2 were not seen in frog heart, an observation which confirms the absence of T tubules in this amphibian. It is concluded that, in mammalian cardiac muscle, the lumens of the longitudinal tubules are continuous with the lumens of the T tubules, forming an extensively interconnected T-L tubular system. Hence, every myofibril has close access to a fluid-filled space which is continuous with the interstitial fluid and which may be of similar cationic composition; such an arrangement should facilitate excitation-contraction coupling.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00332855
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