title: Comparison of the organization of T-tubules, sarcoplasmic reticulum and ryanodine receptors in rat and human ventricular myocardium.
abstract: 1. It is apparent from the literature that there are significant differences in excitation-contraction coupling between species, particularly in the density of calcium transporting proteins in the t-system and sarcoplasmic reticulum (SR) Ca(2+)  release channels. Unfortunately, there is a lack of information as to how the principal structures that link electrical excitation to the activation of calcium-induced calcium release (CICR) are different between human and animal models (particularly rat). 2. Comparison of wheat germ agglutinin and caveolin-3 labelling revealed a non-uniform distribution of surface membrane glycosylation in the rat, rabbit and human, and that the rat t-system appeared more complex in geometry than the latter species. Analysis of the t-system skeleton showed that the t-system was highly branched in the rat compared with that of the human (0.8 ± 0.08 and 0.2 ± 0.07 branch points per μm(2) , respectively; P < 0.001). 3. We also compared the distribution of contractile machinery, sodium-calcium exchange, SR and ryanodine receptors (RyR) in rat and human. F-Actin and RyR labelling was used to estimate the area of contractile apparatus supplied by each RyR cluster. In the rat, each RyR cluster supplied an average cross-sectional area of contractile machinery of 0.36 ± 0.03μm(2)  compared with 0.49 ± 0.04 μm(2)  in human (P = 0.048). Sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA2a) labelling showed that the SR formed a tight network of loops surrounding contractile fibrils that were denser than the t-tubule network, but otherwise appeared similar in both species. 4. In general, the results show a higher density in structures involved in CICR in the rat compared with human.
authors.affiliation: Department of Physiology, School of Medical Sciences, University of Auckland, Auckland, New Zealand.
authors.forename: Id
authors.initials: I
authors.lastname: Jayasinghe
authors.forename: Dj
authors.initials: Dj
authors.lastname: Crossman
authors.forename: C
authors.initials: C
authors.lastname: Soeller
authors.forename: Mb
authors.initials: M
authors.lastname: Cannell
mesh_terms: D000368:Aged; D000818:Animals; D006352:Heart Ventricles / Q000737:chemistry / Q000166:cytology* / Q000378:metabolism; D006801:Humans; D008870:Microtubules / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D008875:Middle Aged; D009206:Myocardium / Q000737:chemistry / Q000166:cytology* / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000737:chemistry* / Q000502:physiology; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D012519:Sarcoplasmic Reticulum / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000737:chemistry / Q000502:physiology; D013045:Species Specificity
chemical_list: D019837:Ryanodine Receptor Calcium Release Channel; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases