ABSTRACT
The ultrastructure of the relationship between the sarcoplasmic (SR) and the intercalated disk in the atrial myocardial cells of the heart is studied. The results reveal: a coupling exists between the SR and the unspecializsd sarcolem-ma of the intercalated disk. In order to differentiate it from a general peripheral coupling it is called intercalated disk coupling. It possesses 3 morphological features of the peripheral and interior couplings, i. e., the cytoplasmic gap in coupling region is about 11-18 nm in width; the jnctional processes or junc-tional feet are located in the cytoplasmic gap; and the SR contains electronic dense material in its lumen. In the coupling region the RS membranes are not only coupling with the unspecialized membrane of the intercalated disk but also closely apposed to the external membrane of mitochondria. In addition, the gap junction-sarcoplasmic reticulum couplings are formed between the cardial gap junction and the SR. Its ultrastructural characteristics are the same as the cardial couplings. The functional significance of the couplings of the SR with the intercalated disk is discussed.
ABSTRACT
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.