Abstract
The ultrastructural basis of Starling's law is well established in the adult. We have demonstrated age-related changes in left (LV) and right (RV) ventricular function in the newborn lamb. To determine whether these changes in function were related to maturational changes in sarcomere length (SL), we assessed myocardial ultrastructure in 12 lambs (1-22 days). Representative sections were excised from mid-lateral walls of LV and RV following cardiac arrest with KCL. Tissue was fixed in modified Karnofsky solution and paraformaldehyde, post-fixed in OsO4, dehydrated in acetone and imbedded in Epon 812. Sections were examined by light microscopy for longitudinal orientation. Electronmicrographs were prepared from representative areas. At birth LV and RV myocardium was poorly organized with small thin myofibrils and a large proportion of non-contractile elements (mitochondria, nuclei and glycogen). With maturation, organization and relative proportions of contractile material increased more rapidly for LV than RV. Myofibrillar diameter (MFD) also increased more rapidly for LVthan RV (MFD-4 weeks/MFD-NB=1.8 for LV; 1.2 for RV). At all ages, RV and LV SL were the same (1.7 1.85 microns). Thus, previously shown age-related differences in LV and RV function are not the result of maturational changes in sarcomere length.
(Sponsor: F.H. Adams)
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Riemenschneider, T., Burks, D., Brenner, R. et al. MYOCARDIAL ULTRASTRUCTURE IN LAMBS: COMPARISON OF SARCOMERE LENGTH AND INTRACELLULAR ORGANIZATION. Pediatr Res 11, 398 (1977). https://doi.org/10.1203/00006450-197704000-00174
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DOI: https://doi.org/10.1203/00006450-197704000-00174