MORPHOMETRY AND AUTORADIOGRAPHY OF EARLY HYPERTROPHIC CHANGES IN VENTRICULAR MYOCARDIUM OF ADULT RAT - ELECTRON-MICROSCOPIC STUDY

  • 1 January 1976
    • journal article
    • research article
    • Vol. 35  (5) , 475-483
Abstract
The ultrastructural composition of left ventricular myocardium and myocytes was investigated 20 h after the surgical production of a subdiaphragmatic aortic stenosis in the adult rat. Morphometric analysis showed a 20% increase in the size of myocytes resulting principally from a 36% increase in mitochondrial volume and a 78% increase in the volumes occupied by smooth endoplasmic reticulum and matrix. Myofibrillar volume is increased only 4%. Measurements of the size and shape of individual mitochondria indicated that the augmentation of this compartment is wholly accountable by the enlargement of preexisting mitochondria. Quantitative autoradiographic analysis following a 2-h pulse labeling with 3H-leucine showed that the rate of incorporation of newly synthesized proteins is practically uniform throughout all structural components of the sarcoplasm 18-20 h after aortic banding. This interval of hypertrophic response is a transition period characterized by an increasing rate of synthesis of contractile proteins overtaking a previously greater rate of mitochondrial synthesis.