The Effects of Progesterone Administration on Hepatic Endoplasmic Reticulum: An Electron Microscopic and Biochemical Study

It is now well known that there are tiny membrane-limited channels ramifying throughout the cytoplasm of most cells. Porter (24) was the first to describe this lace-like reticulum of membranes with the electron microscope. Because of its association with the endoplasmic portion of the cell rather than the ectoplasm, it was referred to as the “endoplasmic reticulum” (25,26). In 1955, Fawcett (7) noted that two forms of the endoplasmic reticulum existed in the hepatic parenchymal cell. One form consisted of a system of membranes studded with ribosomes (rough-surfaced endoplasmic reticulum) and the other consisted of only a membranous network (smooth-surfaced endoplasmic reticulum).