The membrane association among the rough-and smooth-surfaced endoplasmic reticulum and Golgi apparatus in rat hepatocytes at certain circadian stages.

Subcellular structures of the cytoplasmic components in perilobular hepatocytes were examined at 0500 h and 1700 h in 6 adult male Wistar rats per time period. At both time points, the endoplasmic reticulum (ER) having smooth and rough parts could clearly be observed. Corresponding to the decrease and increase of the smooth-surfaced endoplasmic reticulum (sER) during the 24-hr span, it is thought that the membrane transformation from the sER to rough-surfaced endoplasmic reticulum (rER) at 0500 h and from the rER to sER at 1700 h occurs in the flowing-off of membranes which is accompanied by attachment or detachment of ribosomes. Furthermore, at these time points, the direct continuity of membranes between the rER and Golgi apparatus is discerned. From these findings, it may be elicited that the membrane association among the cytoplasmic components takes an important role in the reorganization of the cytoplasmic components in hepatocytes during the 24-hr span.