Objective To study the regularities of myocardiac cells with age increasing. Methods 30 male rats were used in the experiment and divided into three groups:infant group (20\|25 day), young group (3\|5 month) and old group (13\|15 month). Routine paraffine sections were made for PTAH staining and data of cell area, nuclear area, ratio of nucleus to cytoplasm, nuclear ellipticity were measured by image computer analyzer. Results With advancing age:1\^ Cell area and nuclear area became larger; the ratio of nucleus to cytoplasm was declined; nuclear ellipticity turned high. 2\^The cell area of ventricular myocytes was bigger than that of atrial myocytes, the cell area of left atrial myocytes and left ventricular myocytes was bigger than that of right ones, and the cell area of interventricular septum was between that of right ventricular myocytes and left ones. 3\^ Myocardiac cells became thicker and longer; intercalated disc got distinct and complex.Conclusion The growth of nuclei seem to slower than that of myocardiac cells; the morphology of nucleus changes from round to ellipse; Round nucleus is one of important features of young cells; the cells in atrium is younger than that of ventricle.

Objective To investigate the change of Connexin43 expression in rat heart as age advancing. Methods The expressions of Connexin43 in different age of rat heart were determined by immunohistochemistry. Results 1\^ The expression of Connexin43 was only seen in ventricular myocardium. 2\^ The Connexin43 immunolabelling of infant rat heart lie much more within the transversely orientated intercalated disk, besides, a fewer have a punclate distribution over the entire surface of the ventricular myocytes, and Connexin43 distributed mainly on the myocyte surface of the parpillary muscles. Connexin43 immunolabelling of young and old rat heart are typically confined to the site of intercalated disk.Conclusion The expressions of Connexin43 are different in different age and different parts of rat heart.