Objective To research the spatiotemporal pattern of N-cadherin expression during development of rat cardiomyocytes and age-related changes of N-cadherin expression. Methods Using immunohistochemical method,myocardial N-cadherins distribution was investigated in fetal rat and postnatal development(1 postnatal day to old rat),and quantitied by HIPAS-1000 computerized image analytical instrument. Results The expression of N-cadherin was located in myocardium of atrial and ventricule and septum interventriculare and papillary muscles.The N-cadherin immunolabeling was found in myocyte membranes and within cytoplasm in fetal rat heart.From neonatal to infant rat,the pattern of N-cadherin immunolabeling changed progressively,from being dispersed over the entire cell surface as in the fetal to the transverse terminals of the myocytes,toward the distribution within the intercalated disk.From young to old rat heart,the typical N-cadherin was located in transversely orientated intercalated disk.The percentage of N-cadherin immune postive area in rat ventricular myocardium showed a progressively changement with age.Conclusion The present paper demonstrated that the N-cadherin expression exists progressively with ages and the changing pattern of N-cadherin is closely related with development of the intercalated disk in rat myocardium.The mechanical coupling provided by adherens junctions is essential for the stable cell-cell contact.

BACKGROUND: Macula adherens protein is found closely associated with congenital cardiac malformation and myocardial differentiation. OBJECTIVE: To investigate the expression characteristics of α-macula adherens protein in rat heart, as well as the property of age-dependant expression during myocardial growth. DESIGN: Randomized controlled, observational comparative study. SETTING: Department of Cell Biology of Xinxiang Medical College; Department of Bioengineering and Agricultural Economics of Puyang Vocational Technical School. MATERIALS: This study was conducted at the Morphological Laboratory of Xinxiang Medical College between January and June 2003. Totally 28 Wistar rats of clean grade were divided into infant group, youth group,middle-age group, and old-age group with 7 rats in each group. METHODS: All rats were anaesthetized and then cardiac tissues were cut into consecutive coronal slices of 5 μm thick. The expression of α-macula adherens protein in rat myocardium of infant, youth, middle-age and oldage groups was detected using IHC method. The positive cells displayed brownish yellow granules on the surface, cytoplasm and intercalated disc. Routine HE staining was performed on all specimens for structural comparison. MAIN OUTCOME MEASURES: The expression of α-macula adherens protein in rat myocardium of different groups. RESULTS: All the 28 rats entered the final results analysis. ① α-macula adherens protein was found to be expressed in myocardium in atrium, ventricle, papilla muscles and interventricular septum. ② In infant rats, the expression of α-macula adherens protein was mainly observed in intercalated disc at the end of myocardium, with less expression on cell surface and in cytoplasm; in contrast, α-macula adherens protein in young, middleaged and old rats was found to be typically expressed in intercalated disc at the end of myocardium. CONCLUSION: The expression of α-macula adherens protein displays age-dependant manner during rat myocardial development; moreover, the expression of α-macula adherens protein is found to be consistent with the development of intercalated disc.

Objective To investigate the differences of connexin 43(Cx43)expression between adult and infant heart. Methods By using immunohistochemistry to observe the expression of Cx43. Results 1.The expression of Cx43 had a punclate distribution in cytoplasm and over the entire surface of the cardiocyte,and a few located at intercalated disk of atrial and ventricular myocardium in the infant heart.2.Cx43 positive granules distributed irregularly in cell side surface and cytoplasm as well as intercalated disk in adult atrium.Cx43 immunolabelling of adult ventricular myocardium was typically confined to the site of intercalated disk.3.The results of image analyzer showed that the amount of connexin43 expression was lower in the atrium than that of the ventricle in infant heart and atrium bigger than ventricle in adult heart.The expression of Cx43 was less in adult heart than that of infant heart.Conclusion The expression of Cx43 was mainly over the entire surface of the myocardium in infant heart.There were expression differences of Cx43 in human ventricular and atrial myocytes.The amount of Cx43 expression was higher in ventricle than that of atrium in infant heart and atrium bigger than ventricle in adult heart.It was less in adult heart than that of infant.It showed that the expression of Cx43 in human heart existed a developmental differences.