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Journal of Muscle Research and Cell Motility

, Volume 28, Issue 2–3, pp 115–121 | Cite as

T-tubule profiles in Purkinje fibres of mammalian myocardium

  • Alessandro Di Maio
  • H. E. Ter Keurs
  • Clara Franzini-Armstrong
Original Paper

Abstract

Purkinje (P)-fibres are cardiac myocytes that are specialized for fast conduction of the electrical signal. P-fibres are usually defined as having the following identifying features: lack of T tubules; frequent lateral cell junctions; deep indentations at the intercalated discs level; the CX40 isoforms of gap junction proteins and, in large mammals, paucity of myofibrils and abundance of glycogen. We have examined the ultrastructure of P-fibres in free running P-strands from right and left ventricles of small (mouse and rat) intermediate (rabbit) and large (dog) size mammals focusing on presence and distribution of the T tubules. In contrast with previous studies, we find that P-fibres do have T tubules which form normal dyadic associations with the sarcoplasmic reticulum and that the frequency of tubules varies with the size of the animal. Profiles of T tubules and dyads are present over short segments of individual P-cells flanked by totally T tubule-free segments. It is thought that lack of T tubules in P-cells is necessary to reduce capacitance and thus accelerate action potential spread. This may not be as important in a small heart.

Keywords

Transverse (T) tubule Purkinje (P) strands Purkinje (P) cells Sarcoplasmic reticulum Action potential 

Notes

Acknowledgements

We thank Ms. Nosta Glaser for her help during the experiments and photography, Dr. Didier Brochet for his help on the rabbit heart and Dr. Boyden for her very helpful suggestions. This work was supported by NIH grant HL48093.

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Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  • Alessandro Di Maio
    • 1
    • 2
  • H. E. Ter Keurs
    • 3
  • Clara Franzini-Armstrong
    • 1
  1. 1.Department of Cell & Developmental BiologyUniversity of Pennsylvania, School of MedicinePhiladelphiaUSA
  2. 2.Department of Physiological SciencesNational Institute of Fitness and Sports KanoyaKagoshimaJapan
  3. 3.Department of Physiology, School of MedicineUniversity of CalgaryCalgaryCanada

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